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{{Short description|American nuclear fusion facility}} | |||
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{{Use mdy dates|date=December 2022}} | |||
{{Use American English|date=December 2022}} | |||
]|alt=A large building]] | |||
] experiment is mounted in the ] target positioning system, or cryoTARPOS. The two triangle-shaped arms form a shroud around the cold target to protect it until they open five seconds before a shot.|alt=refer to caption]] | |||
The '''National Ignition Facility''' ('''NIF''') is a ]-based ] (ICF) research device, located at ] in ], United States. NIF's mission is to achieve ] with high ]. It achieved the first instance of scientific ] controlled fusion in an experiment on December 5, 2022, with an energy gain factor of 1.5.<ref name=":1">{{Cite journal |last=Clery |first=Daniel |date=December 13, 2022 |title=With historic explosion, a long sought fusion breakthrough |url=https://www.science.org/content/article/historic-explosion-long-sought-fusion-breakthrough |access-date=December 13, 2022 |website=] |doi=10.1126/science.adg2803 |archive-date=December 24, 2022 |archive-url=https://web.archive.org/web/20221224013859/https://www.science.org/content/article/historic-explosion-long-sought-fusion-breakthrough |url-status=live }}</ref><ref>{{citation |journal=] |publisher=American Institute of Physics |title=National Ignition Facility surpasses long-awaited fusion milestone |author=David Kramer |date=December 13, 2022 |volume=2022 |issue=2 |pages=1213a |doi=10.1063/PT.6.2.20221213a |bibcode=2022PhT..2022b1213. |s2cid=254663644 |quote=The shot at Lawrence Livermore National Laboratory on 5 December is the first-ever controlled fusion reaction to produce an energy gain. |url=https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/ |access-date=December 13, 2022 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608084103/https://pubs.aip.org/physicstoday/Online/41898/National-Ignition-Facility-surpasses-long-awaited |url-status=live }}</ref> It supports ] and design by studying the ] under the conditions found within nuclear explosions.<ref>{{cite web|url=https://lasers.llnl.gov/about/ |title=About NIF & Photon Science|archive-url=https://web.archive.org/web/20171202182709/https://lasers.llnl.gov/about |archive-date=December 2, 2017 |publisher=Lawrence Livermore National Laboratory}}</ref> | |||
The '''National Ignition Facility''', or '''NIF''', is a high-energy, high-power ] research device under construction at the ], in ]. Its main roles will be the exploration of ] and, through these experiments, exploring high-energy high-density physics and ]s for the ]. | |||
NIF is the largest and most powerful ICF device built to date.<ref>{{Cite journal |last1=Hogan |first1=W.J |last2=Moses |first2=E.I |last3=Warner |first3=B.E |last4=Sorem |first4=M.S |last5=Soures |first5=J.M |date=2001 |title=The National Ignition Facility |url=https://iopscience.iop.org/article/10.1088/0029-5515/41/5/309 |journal=Nuclear Fusion |volume=41 |issue=5 |pages=567–573 |doi=10.1088/0029-5515/41/5/309 |bibcode=2001NucFu..41..567H |s2cid=250785362 |issn=0029-5515 |access-date=December 17, 2022 |archive-date=December 17, 2022 |archive-url=https://web.archive.org/web/20221217015411/https://iopscience.iop.org/article/10.1088/0029-5515/41/5/309 |url-status=live }}</ref> The basic ICF concept is to squeeze a small amount of fuel to reach pressure and temperature necessary for fusion. NIF hosts the world's most energetic ]. The laser indirectly heats the outer layer of a small sphere. The energy is so intense that it causes the sphere to implode, squeezing the fuel inside. The implosion reaches a peak speed of {{convert|350|km/s|mm/ns|abbr=on}},<ref>{{cite web |url=https://www.theengineer.co.uk/tracing-the-sources-of-nuclear-fusion/ |first=Stuart |last=Nathan |title=Tracing the sources of nuclear fusion |website=The Engineer |date=October 6, 2019 |access-date=June 10, 2019 |archive-date=June 10, 2019 |archive-url=https://web.archive.org/web/20190610021144/https://www.theengineer.co.uk/tracing-the-sources-of-nuclear-fusion/ |url-status=live }}</ref> raising the fuel density from about that of water to about 100 times that of ]. The delivery of energy and the ] during implosion raises the temperature of the fuel to hundreds of millions of degrees. At these temperatures, fusion processes occur in the tiny interval before the fuel explodes outward. | |||
Construction of the NIF has been fraught with problems; compared to initial estimates, NIF is over seven years behind schedule and almost ten times over budget. Its potential role in ] research has also made it a controversial political topic. As of May 2006, sixteen of the lasers (out of a planned 192) had been completed. Construction of the NIF is currently estimated to be completed in 2009 with the first fusion ignition tests planned for 2010. | |||
Construction on the NIF began in 1997. NIF was completed five years behind schedule and cost almost four times its original budget. Construction was certified complete on March 31, 2009, by the ].<ref name="Certified complete">{{cite web |title=Department of Energy Announces Completion of World's Largest Laser |url=https://www.energy.gov/news2009/7191.htm |publisher=] |date=March 31, 2009 |access-date=April 1, 2009 |archive-url=https://web.archive.org/web/20090401194726/http://www.energy.gov/news2009/7191.htm |archive-date=April 1, 2009}}</ref> The first large-scale experiments were performed in June 2009<ref name="firstshots">{{cite web |title=First NIF Shots Fired to Hohlraum Targets |url=https://lasers.llnl.gov/newsroom/project_status/2009/june.php |publisher=National Ignition Facility |date=June 2009 |access-date=September 13, 2009 |archive-url=https://web.archive.org/web/20100528000229/https://lasers.llnl.gov/newsroom/project_status/2009/june.php |archive-date=May 28, 2010}}</ref> and the first "integrated ignition experiments" (which tested the laser's power) were declared completed in October 2010.<ref name="Oct8_10">{{cite web |title=First successful integrated experiment at National Ignition Facility announced |work=General Physics |publisher=PhysOrg.com |date=October 8, 2010 |url=http://www.physorg.com/news205740709.html |access-date=October 9, 2010 |archive-date=December 13, 2022 |archive-url=https://web.archive.org/web/20221213172710/http://www.physorg.com/news205740709.html |url-status=live }}</ref> | |||
==Background== | |||
:''Main article: ]'' | |||
From 2009 to 2012 experiments were conducted under the National Ignition Campaign, with the goal of reaching ignition just after the laser reached full power, some time in the second half of 2012. The campaign officially ended in September 2012, at about {{frac|10}} the conditions needed for ignition.<ref>{{cite tech report |last=Crandall |first=David |title=Final Review of the National Ignition Campaign |url=http://fire.pppl.gov/NIF_NIC_rev6_Koonin_2012.pdf |date=December 27, 2012 |publisher=Department of Energy |page=3}}</ref><ref>{{cite book |title=An Assessment of the Prospects for Inertial Fusion Energy |url=https://books.google.com/books?id=lBKfAwAAQBAJ |publisher=National Academies Press |date=July 2013 |page=2 |isbn=978-0-309-27224-7}}</ref> Thereafter NIF has been used primarily for materials science and weapons research. In 2021, after improvements in fuel target design, NIF produced 70% of the energy of the laser, beating the record set in 1997 by the ] reactor at 67% and achieving a ].<ref name=":0" /> On December 5, 2022, after further technical improvements, NIF reached "ignition", or ], for the first time, achieving a 154% energy yield compared to the input energy.<ref name="igntion2022-llnl" /> However, while this was scientifically a success,<ref name=":6">{{Cite web |date=2022-12-13 |title=We have 'ignition': Fusion breakthrough draws energy gain |url=https://www.nbcnews.com/science/science-news/fusion-breakthrough-net-energy-gain-rcna61326 |access-date=2024-07-10 |website=NBC News |language=en}}</ref> the experiment in practice produced less than 1% of the energy the facility used to create it:<ref name=":5">{{Cite web |date=2022-12-13 |title=There is no "breakthrough": NIF fusion power still consumes 130 times more energy than it creates |url=https://bigthink.com/the-future/fusion-power-nif-hype-lose-energy/ |access-date=2024-07-10 |website=Big Think |language=en-US}}</ref> while 3.15 MJ of energy was yielded from 2.05 MJ input,<ref name=":4">{{Cite web |title=Why the nuclear fusion 'net energy gain' is more hype than breakthrough |url=https://whyy.org/segments/why-the-nuclear-fusion-net-energy-gain-is-more-hype-than-breakthrough/ |access-date=2024-07-10 |website=WHYY |language=en-US}}</ref> the lasers delivering the 2.05 MJ of energy took about 300 MJ to produce in the facility.<ref name=":6" /> | |||
The basic idea behind any ] (ICF) device is to rapidly heat the outer layers of a "target", a small plastic sphere containing a few milligrams of fusion fuel, typically a mix of ] and ]. The heat burns the plastic into a ], which explodes off the surface. Due to ], the remaining portion of the target is driven inwards, eventually collapsing into a small point of very high density. The rapid blowoff also creates a ] that travels towards the center of the compressed fuel. When it meets itself in the center of the fuel, the energy in the shock wave further heats and compresses the tiny volume around it. If the temperature and density of that small spot is raised high enough, fusion reactions will occur. | |||
== Inertial confinement fusion basics == | |||
The fusion reactions release high-energy particles, which collide with the high density fuel around it and slow down. This heats the fuel further, and can potentially cause that fuel to undergo fusion as well. Given the right overall conditions of the compressed fuel—high enough density and temperature—this heating process can result in a ], burning outward from the center where the shock wave started the reaction. This is a condition known as "ignition", which can lead to a significant portion of the fuel in the target undergoing fusion, and the release of significant amounts of energy. | |||
{{Main|inertial confinement fusion#ICF mechanism of action|l1=ICF mechanism}} | |||
] | |||
] | |||
] (ICF) devices use intense energy to rapidly heat the outer layers of a target in order to compress it. Nuclear fission provides the energy source for thermonuclear warheads, while sources such as laser beams and particle beams are used in non-weapon devices.<ref name=FW>{{citation |last=Winterberg |first=Friedwardt |page=2 |title=The Release of Thermonuclear Energy by Inertial Confinement: Ways Towards Ignition |date=2010 |publisher=World Scientific |isbn=978-981-4295-90-1 }}</ref> | |||
The target is a small spherical pellet containing a few milligrams of fusion fuel, typically a mix of ] (D) and ] (T), as this composition has the lowest ignition temperature.{{r|FW}} | |||
To date most ICF experiments have used lasers to heat the targets. Calculations show that the energy must be delivered quickly in order to compress the core before it disassembles, as well as creating a suitable shock wave. The laser beams must also be focused evenly across the target's outer surface in order to collapse the fuel into a symmetric core. Although other "drivers" have been suggested, lasers are currently the only devices with the right combination of features. | |||
The lasers can either heat the surface of the fuel pellet directly – known as ''direct drive'' – or heat the inner surface of a hollow metal cylinder around the pellet – known as ''indirect drive''. In the indirect drive case, the cylinder, called a '']'' (German for 'hollow room' or 'cavity'), becomes hot enough to re-emit the energy as even higher frequency ]s. These X-rays, which are more symmetrically distributed than the original laser light, heat the surface of pellet. | |||
==Description== | |||
In either case, the material on the outside of the pellet is turned into a ], which explodes away from the surface. The rest of the pellet is driven inward on all sides, into a small volume of extremely high density. The surface explosion creates ]s that travel inward. At the center of the fuel, a small volume is further heated and compressed. When the temperature and density are high enough, fusion reactions occur.<ref name="how">{{cite web|url=https://lasers.llnl.gov/programs/nif/how_nif_works/ |title=How NIF works|archive-url=https://web.archive.org/web/20100527191346/https://lasers.llnl.gov/programs/nif/how_nif_works/ |archive-date=May 27, 2010|publisher=Lawrence Livermore National Laboratory|access-date=October 2, 2007}}</ref> The energy must be delivered quickly and spread extremely evenly across the target's outer surface in order to compress the fuel symmetrically.<ref>{{cite journal|title=Azimuthal Drive Asymmetry in Inertial Confinement Fusion Implosions on the National Ignition Facility|author=Hans G. Rinderknecht |author2=D. T. Casey |author3=R. Hatarik |author4=R. M. Bionta |author5=B. J. MacGowan |author6=P. Patel |author7=O. L. Landen |author8=E. P. Hartouni |author9=O. A. Hurricane |journal=]|volume=124|number=145002 |date=10 April 2020|page=145002 |doi=10.1103/PhysRevLett.124.145002|pmid=32338973 |bibcode=2020PhRvL.124n5002R |s2cid=216305472 |quote=symmetry degrades hot-spot conditions at peak convergence and limits implosion performance and yield.|doi-access=free}}</ref> | |||
] | |||
In order to make this process efficient, the compression must be extremely symmetrical, a process that has been a major design problem with previous ICF attempts. To address this, NIF aims to create a single ultrabright flash of light that reaches the target from several directions at precisely the same time. The original design called for a single laser source to be redirected into 256 "beamlines", each of which would amplify the power of this single source through a series of 19 neodymium-doped phosphate glass amplifiers. During one of several redesigns the number of beamlines and amplifiers was reduced to the current design's 192 beamlines and 16 amplifiers per line.<ref name=how>(March 2006}. "". ''Lawrence Livermore National Laboratory''. Retrieved on ] ].</ref> This number is nonetheless far and away beyond the number and size of beams of any preceding ICF laser. | |||
The reactions release high-energy particles, some of which, primarily ]s, collide with unfused fuel and heat it further, potentially triggering additional fusion. At the same time, the fuel is also losing heat through ] losses and hot electrons leaving the fuel area. Thus the rate of alpha heating must be greater than the loss rate, termed ''bootstrapping''.<ref name="hurricane">{{cite web |url=https://www.llnl.gov/news/climbing-mountain-fusion-ignition-interview-omar-hurricane |title=Climbing the mountain of fusion ignition: an interview with Omar Hurricane |website=LLNL |access-date=May 29, 2015 |archive-date=December 13, 2022 |archive-url=https://web.archive.org/web/20221213223929/https://www.llnl.gov/news/climbing-mountain-fusion-ignition-interview-omar-hurricane |url-status=live }}</ref> Given the right conditions—high enough density, temperature, and duration—bootstrapping results in a ], burning outward from the center. This is known as ''ignition'', which fuses a significant portion of the fuel and releases large amounts of energy.<ref name="econ">{{cite web |url=http://www.nuc.berkeley.edu/thyd/icf/IFE.html |title=Inertial Fusion Energy: A Tutorial on the Technology and Economics |archive-url=https://web.archive.org/web/20081221233137/http://www.nuc.berkeley.edu/thyd/icf/IFE.html |archive-date=December 21, 2008 |last=Peterson |first=Per F. |date=September 23, 1998 |access-date=October 8, 2013}}</ref> | |||
The initial laser light is provided by the '''Injection Laser System''' (ILS), the original source being created in a ]-doped optical fiber known as the '''Master Oscillator'''. The light from this source is directed into 48 small '''Preamplifier Modules''' (PAMs). The modules pass the light four times through a circuit containing a ] glass amplifier similar to (but much smaller than) the ones used in the main beamlines. The amplifiers operate in the ] region, at 1054 nanometers. The microjoules of light created in the Master Oscillator is boosted to about 10 joules by the time it leaves the PAMs. According to LLNL, the design of the PAMs has been one of the major stumbling blocks during construction.<ref>"". ''Lawrence Livermore National Laboratory''. Retrieved on ] ].</ref> | |||
As of 1998, most ICF experiments had used laser drivers. Other drivers have been examined, such as heavy ions driven by ]s.<ref>Per F. Peterson, , University of California, Berkeley, 1998. Retrieved on May 8, 2008. {{webarchive |url=https://web.archive.org/web/20080506122940/http://www.nuc.berkeley.edu/thyd/icf/target.html |date=May 6, 2008 }}</ref><ref>Per F. Peterson, , University of California, Berkeley, 1998. Retrieved on May 8, 2008. {{webarchive |url=https://web.archive.org/web/20080506200941/http://www.nuc.berkeley.edu/thyd/icf/driver.html |date=May 6, 2008 }}</ref> | |||
The main amplification takes place in a series of glass amplifiers located at one end of the beamlines. Prior to "firing", the amplifiers are first ] by a total of 7,680 ]s (the PAMs have their own smaller pumps as well). The lamps are powered by a ] bank which stores a total of 330 megajoules (MJ) of electrical energy. When the wavefront passes through them, the amplifiers release some of the light energy stored in them into the beam. This is not a particularly efficient process, and in order to improve the energy transfer the beams are sent though the main amplifier section four times, using an optical switch located in a mirrored cavity. In total these amplifiers boost the original 10 J provided by the PAMs to a nominal 4 MJ.<ref name=how/> Given the time scale of a few billionths of a second, the power is correspondingly very high (1000 ]). | |||
== Design == | |||
After the amplification is complete the light is "switched" back into the beamline, where it runs to the far end of the building to the '''Target Chamber'''. The total length of the laser from one end to the other is about 1,000 feet (305 meters). Diagnostic and wave-shaping elements are spread through the entire length of the beamline, which allows the wavefront to be accurately focused in order to ensure that the image of the beam as it reaches the target is extremely uniform. Most of the equipment is packaged into '''Line Replaceable Units''' (LRUs), standardized boxes about the size of a small car that can be dropped out of the beamline for replacement from below.<ref>Larson, Doug W. (2004). "". ''Optical Engineering at the Lawrence Livermore National Laboratory II: The National Ignition Facility.'' ]. Retrieved on ] ].</ref> | |||
=== System === | |||
On reaching the Target Chamber the light is reflected off various turning mirrors in order to impinge on the target from different directions. As can be seen in the layout diagram above, NIF directs the laser into the chamber primarily from the top and bottom. Since the length of the overall path from the Master Oscillator to the target is different for each of the beamlines, optics are used to "slow" the light in order to ensure all of them reach the center within a picosecond of each other. | |||
] of the laser energy to ] ] to target capsule energy coupling efficiency. Note the "laser energy" is after conversion to ], which loses about 50% of the original ] power. The conversion of x-ray heat to energy in the fuel loses another 90% – of the 1.9 MJ of laser light, only about 10 kJ ends up in the fuel itself.]] | |||
NIF primarily uses the indirect drive method of operation, in which the laser heats a small metal cylinder surrounding the capsule inside it, which then emits X-rays that heat the fuel pellet. Experimental systems, including the ] and ]s, validated this approach.<ref>J.D. Lindl et al., '''', Physics of Plasmas, Vol. 11, February 2004, page 339. Retrieved on May 7, 2008.</ref> The NIF's high power supports a much larger target than OMEGA or Nova; the baseline pellet design is about 2 mm in diameter. It is chilled to about 18 kelvin (−255 °C) and lined with a layer of frozen deuterium–tritium (DT) fuel. The hollow interior contains a small amount of DT gas.<ref>{{Cite web|url=https://www.scientificamerican.com/article/high-powered-lasers-deliver-fusion-energy-breakthrough/|title=High-Powered Lasers Deliver Fusion Energy Breakthrough|first=David|last=Biello|website=Scientific American|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215012418/https://www.scientificamerican.com/article/high-powered-lasers-deliver-fusion-energy-breakthrough/|url-status=live}}</ref> | |||
One of the last steps in the process before reaching the target chamber is to convert the infrared light at 1054 nm into the ultraviolet at 351 nm in a device known as a ]. These are made of thin sheets cut from a monocrystal of ] placed in the beamlines. When the laser light passes through them they essentially combine three of the IR photons into a single UV one. IR light is much less effective than UV at heating the targets, because IR couples more strongly with hot ] which will absorb a considerable amount of energy and interfere with compressing the target.<ref>Bibeau, Camille; Paul J. Wegner, Ruth Hawley-Fedder (] ]). "". ''Laser Focus World''. Retrieved on ] ].</ref> The conversion process is about 50% effective, reducing delivered energy to a nominal 1.8 MJ (500 terawatts). | |||
In a typical experiment, the laser generates 3 MJ of infrared laser energy of a possible 4. About 1.5 MJ remains after conversion to UV, and another 15 percent is lost in the hohlraum. About 15 percent of the resulting x-rays, about 150 kJ, are absorbed by the target's outer layers.<ref name="gain">Suter, L.; J. Rothenberg, D. Munro, et al., "", Lawrence Livermore National Laboratory, December 6, 1999. Retrieved on May 7, 2008.</ref> The coupling between the capsule and the x-rays is lossy, and ultimately only about 10 to 14 kJ of energy is deposited in the fuel.<ref>{{cite journal |last1=Hurricane |first1=O. A. |last2=Callahan |first2=D. A. |last3=Casey |first3=D. T. |last4=Dewald |first4=E. L. |last5=Dittrich |first5=T. R. |last6=Döppner |first6=T. |last7=Barrios Garcia |first7=M. A. |last8=Hinkel |first8=D. E. |last9=Berzak Hopkins |first9=L. F. |last10=Kervin |first10=P. |last11=Kline |first11=J. L. |date=May 2014 |title=The high-foot implosion campaign on the National Ignition Facility |journal=Physics of Plasmas |volume=21 |issue=5 |page=056314 |bibcode=2014PhPl...21e6314H |doi=10.1063/1.4874330 |osti=1129989 |last12=Pape |first12=S. Le |author13-link=Tammy Ma |last13=Ma |first13=T. |last14=MacPhee |first14=A. G. |last15=Milovich |first15=J. L. |last16=Moody |first16=J. |last17=Pak |first17=A. E. |last18=Patel |first18=P. K. |last19=Park |first19=H.-S. |last20=Remington |first20=B. A. |last21=Robey |first21=H. F. |last22=Salmonson |first22=J. D. |last23=Springer |first23=P. T. |last24=Tommasini |first24=R. |last25=Benedetti |first25=L. R. |last26=Caggiano |first26=J. A. |last27=Celliers |first27=P. |last28=Cerjan |first28=C. |last29=Dylla-Spears |first29=R. |last30=Edgell |first30=D. |last31=Edwards |first31=M. J. |last32=Fittinghoff |first32=D. |last33=Grim |first33=G. P. |last34=Guler |first34=N. |last35=Izumi |first35=N. |last36=Frenje |first36=J. A. |last37=Gatu Johnson |first37=M.|author37-link=Maria Gatu Johnson |last38=Haan |first38=S. |last39=Hatarik |first39=R. |last40=Herrmann |first40=H. |last41=Khan |first41=S. |last42=Knauer |first42=J. |last43=Kozioziemski |first43=B. J. |last44=Kritcher |first44=A. L. |last45=Kyrala |first45=G. |last46=Maclaren |first46=S. A. |last47=Merrill |first47=F. E. |last48=Michel |first48=P. |last49=Ralph |first49=J. |last50=Ross |first50=J. S. |last51=Rygg |first51=J. R. |last52=Schneider |first52=M. B. |last53=Spears |first53=B. K. |last54=Widmann |first54=K. |last55=Yeamans |first55=C. B.}}</ref> | |||
==NIF and ICF== | |||
] | |||
The name "NIF" refers to the goal of "igniting" the fusion fuel, a long-sought threshold in fusion research. In existing (non-weapon) fusion experiments the heat produced by the fusion reactions rapidly escapes from the plasma, meaning that external heating must be applied continually in order to keep the reactions going. Ignition refers to the point where the rate of fusion is high enough that the heat generated by the fusion reaction itself is enough to continually sustain the continued fusing of the surrounding fuel. In this case the majority of the fuel undergoes a "burn", in much the same way wood will burn to ash after being ignited by a match. Ignition is considered a key requirement if ] is to ever become practical. | |||
The fuels in the center of the target are compressed to a density of about 1000 g/cm<sup>3.</sup><ref name="density">{{Cite web |title=Ignition Physics Program |archive-url=https://web.archive.org/web/20060115042042/http://www7.nationalacademies.org/bpa/PLSC_Sept05_Presentation_Lindl.pdf |access-date=August 1, 2022 |last=Lindl |first=John |url=http://www7.nationalacademies.org/bpa/PLSC_Sept05_Presentation_Lindl.pdf |publisher=Lawrence Livermore National Laboratory |date=September 24, 2005 |archive-date=January 15, 2006}}</ref> For comparison, ] has a density of about 11 g/cm<sup>3</sup>. The pressure is the equivalent of 300 billion ].<ref name="hurricane" /> | |||
NIF uses the ''indirect drive'' method of operation, in which the laser heats a small metal cylinder instead of the capsule inside it. The heat causes the cylinder, known as a '']'', to re-emit the energy as intense ]s, which are more evenly distributed and symmetrical than the original laser beams. experimental systems, including the ] and ]s, validated this approach through the late 1980s. In the case of the NIF, the large delivered power allows for the use of a much larger target; the baseline pellet design is about 2 mm in diameter, chilled to about 18 degrees C above absolute zero and lined with a layer of solid ]-] (DT) fuel. The hollow interior also contains a small amount of DT gas. NIF is arranged to shine the laser into the open ends of the hohlraum for conversion into X-rays. | |||
] | |||
Before NIF was constructed, it was expected based on simulations that 10–15 MJ of fusion energy would be released, resulting in a net fusion energy gain, denoted ''Q'', of about 5–8 (fusion energy out/UV laser energy in).<ref>{{cite journal |last1=Krauser |first1=William J. |last2=Hoffman |first2=Nelson M. |last3=Wilson |first3=Douglas C. |last4=Wilde |first4=Bernhard H. |last5=Varnum |first5=William S. |last6=Harris |first6=David B. |last7=Swenson |first7=Fritz J. |last8=Bradley |first8=Paul A. |last9=Haan |first9=Steven W. |last10=Pollaine |first10=Stephen M. |last11=Wan |first11=Alan S. |last12=Moreno |first12=Juan C. |last13=Amendt |first13=Peter A. |title=Ignition target design and robustness studies for the National Ignition Facility |journal=Physics of Plasmas |date=1 May 1996 |volume=3 |issue=5 |pages=2084–2093 |doi=10.1063/1.872006}}</ref> Due to the design of the target chamber, the baseline design limited the maximum possible fusion energy release to 45 MJ,<ref name="target">M. Tobin et al., '''', American Nuclear Society, June 1994. Retrieved on May 7, 2008.</ref> equivalent to about 11 kg of ] exploding.<ref>{{Cite web|url=https://www.qtransform.com/en/table/megajoules-to-tons-of-TNT.htm|title=Table megajoules to tons of TNT | MJ to tTNT|website=www.qtransform.com|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215013240/https://www.qtransform.com/en/table/megajoules-to-tons-of-TNT.htm|url-status=live}}</ref> | |||
This conversion process is fairly efficient, of the original ~4 MJ of laser energy created in the beamlines, 1.8 MJ is left after conversion to UV, and about half of the rest lost in the x-ray conversion in the hohlraum. Of the rest, perhaps 10 to 20% of the resulting x-rays will be absorbed by the outer layers of the target (see image below).<ref name=gain>Suter, L.; J. Rothenberg, D. Munro, et al. (] ]). "". ''Lawrence Livermore National Laboratory''. Retrieved on ] ].</ref> The shockwave created by this heating absorbs about 140 kJ, which is expected to compress the fuel in the center of the target to a density of about 1000 g/mL;<ref name=density>Lindl, John (] ]). "". ''NationalAchademies.org''. Retrived on ] ].</ref> for comparison, ] has a normal density of about 11 g/mL. It is expected this will cause about 20 MJ of fusion energy to be released.<ref name=gain/> Improvements in both the laser system and hohlraum design are expected to improve the shockwave to about 420 kJ, in turn improving the fusion energy to about 100 MJ.<ref name=density/> However the baseline design allows for a maximum of about 45 MJ of fusion energy release, due to the design of the target chamber.<ref name=target></ref> | |||
When NIF was built and used in 2011, the fusion energy was far lower than expected – less than 1 kJ. Performance was gradually improved until, as of 2024, the fusion energy routinely exceeded 2 MJ.<ref>{{cite journal |last1=Rosen |first1=Mordecai D. |title=The long road to ignition: An eyewitness account |journal=Physics of Plasmas |date=1 September 2024 |volume=31 |issue=9 |page=090501 |doi=10.1063/5.0221005}}</ref> | |||
To be useful for energy production, a fusion facility must produce fusion output at least an order of magnitude more than the energy used to power the laser amplifiers – 400 MJ in the case of NIF.<ref>{{cite web|url=https://lasers.llnl.gov/content/assets/docs/news/pk_fun_facts2.pdf|publisher=LLNL|title=NIF By the Numbers|access-date=17 December 2022|archive-date=December 17, 2022|archive-url=https://web.archive.org/web/20221217050603/https://lasers.llnl.gov/content/assets/docs/news/pk_fun_facts2.pdf|url-status=live}}</ref> Commercial laser fusion systems would use much more efficient ], where wall-plug efficiencies of 10 percent have been demonstrated, and efficiencies 16–18 percent were expected with advanced concepts under development in 1996.<ref>{{cite journal |last1=Paine |first1=Stephen |last2=Marshall |first2=Christopher |date=September 1996 |title=Taking Lasers Beyond the NIF |url=https://www.llnl.gov/str/Payne.html |journal=Science and Technology Review |access-date=November 14, 2012 |archive-date=February 27, 2013 |archive-url=https://web.archive.org/web/20130227054624/https://www.llnl.gov/str/Payne.html |url-status=live }}</ref> | |||
NIF was primarily designed as an indirect drive device. Nevertheless, the energy in the laser is high enough to be used as a "''direct drive''" system as well, where the laser shines directly on the target. Even at UV wavelengths the power delivered by NIF is estimated to be more than enough to cause ignition, resulting in fusion energy gains of about forty times, somewhat higher than the indirect drive system. However, as the NIF was designed primarily with hohlraums in mind, the beam layout is arranged to shine into the chamber from the top and bottom, as opposed to from all sides. An additional set of ports is available for these experiments, but changing the system to use them is a time consuming process that makes such experiments unlikely to be scheduled in the short term. | |||
] | |||
=== Laser === | |||
It has recently been shown, using scaled implosions on the OMEGA laser and multidimensional computer simulations, that NIF should also be capable of igniting a capsule, albeit with a lower gain factor, using the so called "''polar direct drive''" (PDD) configuration where the target is irradiated directly by the laser, but only from the top and bottom.<ref name=pdd>Yaakobi, B.; R. L. McCrory, S. Skupsky, et al. (June 1980). "". ''X-Ray Absorption Lines: Signature for Preheat Level in Non-Explosive Laser Implosion - LLE Review'' '''104''': 186-8. Retrieved on ] ].</ref> In this configuration the target suffers either a "pancake" or "cigar" anisotropy on implosion, reducing the maximum temperature at the core. However, the amount of energy being dumped into the target by the laser is so high that it ignites anyway. Fusion gains in this configuration are estimated to be anywhere between ten and thirty times less than the symmetrical direct drive approach, but operable with no changes to the NIF beamline layout. | |||
] | |||
As of 2010 NIF aimed to create a single 500 ] (TW) peak flash of light that reaches the target from numerous directions within a few ]s. The design uses 192 beamlines in a parallel system of flashlamp-pumped, neodymium-doped ] lasers.<ref>{{cite news |title=Press release: NNSA and LLNL announce first successful integrated experiment at NIF |url=https://www.llnl.gov/news/nnsa-and-llnl-announce-first-successful-integrated-experiment-nif |work=Lawrence Livermore National Laboratory |date=October 6, 2010 |access-date=August 12, 2017 |archive-date=August 12, 2017 |archive-url=https://web.archive.org/web/20170812063529/https://www.llnl.gov/news/nnsa-and-llnl-announce-first-successful-integrated-experiment-nif |url-status=live }}</ref> | |||
To ensure that the output of the beamlines is uniform, the laser is amplified from a single source in the Injection Laser System (ILS). This starts with a low-power flash of 1053-nanometer (nm) infrared light generated in an ]-doped optical ] termed Master Oscillator.<ref>P.J. Wisoff et al., '' {{Webarchive |url=https://web.archive.org/web/20150908212244/http://adsabs.harvard.edu/abs/2004SPIE.5341..146W |date=September 8, 2015 }}'', Proceedings of SPIE Vol. 5341, pages 146–155</ref> Its light is split and directed into 48 Preamplifier Modules (PAMs). Each PAM conducts a two-stage amplification process via ]s. The first stage is a regenerative amplifier in which the pulse circulates 30 to 60 times, increasing its energy from nanojoules to tens of millijoules. The second stage sends the light four times through a circuit containing a ] glass amplifier similar to (but much smaller than) the ones used in the main beamlines, boosting the millijoules to about 6 joules. According to LLNL, designing the PAMs was one of the major challenges. Subsequent improvements allowed them to surpass their initial design goals.<ref>{{cite web|url=http://www.llnl.gov/str/Powell.html |title=Keeping Laser Development on Target for the NIF] |author=Powell|archive-url=https://web.archive.org/web/20081204100201/http://www.llnl.gov/str/Powell.html |archive-date=December 4, 2008 }}'', Lawrence Livermore National Laboratory. Retrieved on October 2, 2007</ref> | |||
Certain other targets called "''saturn targets''" are specifically designed to reduce the anisotropy.<ref>True, M. A.; J. R. Albritton, and E. A. Williams (June 1980). "". ''Fast Ion Production by Suprathermal Electrons in Laser Fusion Plasmas - LLE Review'' '''102''': 61-6. Retrieved on ] ].</ref> They feature a small plastic ring around the "equator" of the target, which quickly vaporizes into a plasma when hit by the laser. Some of the laser light is refracted through this plasma back towards the equator of the target, evening out the heating. Ignition with gains just over thirty-five are thought to be possible using these targets on NIF,<ref name=pdd/> producing results almost as good as the fully symmetric direct drive approach. | |||
The main amplification takes place in a series of glass amplifiers located at one end of the beamlines. Before firing, the amplifiers are first ] by a total of 7,680 flash lamps. The lamps are powered by a ] bank that stores 400 MJ (110 kWh). When the wavefront passes through them, the amplifiers release some of the energy stored in them into the beam. The beams are sent through the main amplifier four times, using an ] located in a mirrored cavity. These amplifiers boost the original 6 J to a nominal 4 MJ.<ref name="how" /> Given the time scale of a few nanoseconds, the peak UV power delivered to the target reaches 500 TW.<ref>{{Cite journal|url=https://www.tandfonline.com/doi/full/10.13182/FST94-A40247|title=Laser Design Basis for the National Ignition Facility|first1=J.T.|last1=Hunt|first2=K.R.|last2=Manes|first3=J.R.|last3=Murray|first4=P.A.|last4=Renard|first5=R.|last5=Sawicki|first6=J.B.|last6=Trenholme|first7=W.|last7=Williams|date=November 16, 1994|journal=Fusion Technology|volume=26|issue=3P2|pages=767–771|doi=10.13182/FST94-A40247|bibcode=1994FuTec..26..767H }}</ref> | |||
==Construction problems== | |||
Near the center of each beamline, and taking up the majority of the total length, are '']s''. These consist of long tubes with small telescopes at the end that focus the beam to a tiny point in the center of the tube, where a ] cuts off any stray light outside the focal point. The filters ensure that the beam image is extremely uniform. Spatial filters were a major step forward. They were introduced in the ], an earlier LLNL experiment.<ref>{{Cite web|url=https://lasers.llnl.gov/10-years-of-dedication/laser-leadership|title=45 Years of Laser Leadership|website=lasers.llnl.gov|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215013036/https://lasers.llnl.gov/10-years-of-dedication/laser-leadership|url-status=live}}</ref> | |||
When it was first proposed in 1993, the ] (DOE) estimated NIF was to cost about $667 million dollars, and be completed by 2002. By 1995, still during the planning stages, the estimates had already risen to about $1 billion, and when construction on the main buildings started in May 1997 the number had again crept upward to $1.1 billion. In January 2000 the ] ], then the director of DOE, claimed that the NIF was "on time and within budget", but was soon advised by project managers that neither claim was actually close to the truth. A June 2000 report by DOE further revised their estimate to $2.25 billion, and pushed back the completion date.<ref name=DOE></ref> | |||
The end-to-end length of the path the laser beam travels, including switches, is about {{convert|1500|m|ft}}. The various optical elements in the beamlines are generally packaged into Line Replaceable Units (LRUs), standardized boxes about the size of a ] that can be dropped out of the beamline for replacement from below.<ref>{{cite book |doi=10.1117/12.538467 |bibcode=2004SPIE.5341..127L |chapter=NIF laser line-replaceable units (LRUs) |title=Optical Engineering at the Lawrence Livermore National Laboratory II: The National Ignition Facility |volume=5341 |page=127 |year=2004 |last1=Larson |first1=Doug W. |s2cid=122364719 |chapter-url=https://digital.library.unt.edu/ark:/67531/metadc1410354/ |editor1-last=Lane |editor1-first=Monya A |editor2-last=Wuest |editor2-first=Craig R |access-date=October 11, 2019 |archive-date=December 16, 2022 |archive-url=https://web.archive.org/web/20221216011804/https://digital.library.unt.edu/ark:/67531/metadc1410354/ |url-status=live }}</ref> | |||
In-fighting between the various Department of Energy laboratories soon started, with Sandia and Los Alamos publicly attacking the facility as ill-conceived. On 25 May Sandia vice president Tom Hunter told the '']'' that the NIF should be downsized so that it would not "disrupt the investment needed" in other labs.<ref name=sandia></ref> Criticism of the project also came from | |||
politicians, government officials and review panels, some going so far as to refer to the project as being "out of control".<ref></ref> | |||
After amplification is complete the light is switched back into the beamline, where it runs to the far end of the building to the target chamber. The target chamber is a {{convert|10|m|ft|adj=mid|-diameter}} multi-piece steel sphere weighing {{convert|130000|kg}}.<ref name="Newsweek">{{cite magazine |url=http://www.newsweek.com/id/222792/ |title=Could This Lump Power the Planet? |author=Lyons, Daniel |date=November 14, 2009 |magazine=] |page=3 |access-date=November 14, 2009 |archive-url=https://web.archive.org/web/20091117020847/http://www.newsweek.com/id/222792 |archive-date=November 17, 2009}}</ref> Just before reaching the target chamber, the light is reflected off mirrors in the switchyard and target area in order to hit the target from different directions. Since the path length from the Master Oscillator to the target is different for each beamline, optics are used to delay the light in order to ensure that they all reach the center within a few picoseconds of each other.<ref>Arnie Heller, '' {{Webarchive |url=https://web.archive.org/web/20081121173542/https://www.llnl.gov/str/JulAug05/VanArsdall.html |date=November 21, 2008 }}'', Science & Technology Review, July/August 2005. Retrieved on May 7, 2008</ref> <!-- NIF normally directs the laser into the chamber from the top and bottom.{{cn|date=December 2022}} --> | |||
Given the budget problems, the ] requested an independent review by the ] (GAO). They returned a report in August 2000 stating that the budget was likely $4 billion and was unlikely to be completed anywhere near on time.<ref name=GAO></ref> A follow-up report the next year pushed the budget up again to $4.2 billion, and the completion date to around 2007. | |||
] | |||
In August of 2005, the NIF achieved "first light" on a bundle of 8 beams, producing a 10 nanosecond, 152.8 kJ pulse of IR light, thus eclipsing OMEGA as the highest energy laser (per pulse) on the planet. As of ], sixteen of the eventual 192 lasers had been completed, and by July 2,300 of 6,216 LRUs have been installed.<ref></ref> The lab currently calls for construction to be complete in "1,000 days", which puts the date some time in 2009, with the "Ignition Campaign" starting the next year. Significant effort continues to ensure that this campaign is successful, though by the nature of scientific research its success cannot be guaranteed. | |||
One of the last steps before reaching the target chamber is to convert the infrared (IR) light at 1053 nm into the ultraviolet (UV) at 351 nm in a device known as a ].<ref>P.J. Wegner et al.,'' {{Webarchive |url=https://web.archive.org/web/20150908212244/http://adsabs.harvard.edu/abs/2004SPIE.5341..180W |date=September 8, 2015 }}'', Proceedings of SPIE 5341, May 2004, pages 180–189.</ref> These are made of thin sheets (about 1 cm thick) cut from a single crystal of ]. When the 1053 nm (IR) light passes through the first of two of these sheets, frequency addition converts a large fraction of the light into 527 nm light (green). On passing through the second sheet, frequency combination converts much of the 527 nm light and the remaining 1053 nm light into 351 nm (UV) light. ] (IR) light is much less effective than UV at heating the targets, because IR couples more strongly with hot ] that absorb a considerable amount of energy and interfere with compression. The conversion process can reach peak efficiencies of about 80 percent for a laser pulse that has a flat ] shape, but the temporal shape needed for ignition varies significantly over the duration of the pulse. The actual conversion process is about 50 percent efficient, reducing delivered energy to a nominal 1.8 MJ.<ref>Bibeau, Camille; Paul J. Wegner, Ruth Hawley-Fedder (June 1, 2006). "". ''Laser Focus World''. Retrieved on May 7, 2008.</ref> | |||
These delays have led to something of a race with the French ], which has very similar energies as NIF. Mégajoule started construction later than NIF but has a shorter planned building time, estimated to be complete in 2010. | |||
As of 2010, one important aspect of any ICF research project was ensuring that experiments could be carried out on a timely basis. Previous devices generally had to cool down for many hours to allow the flashlamps and laser glass to regain their shapes after firing (due to thermal expansion), limiting their use to one or fewer firings per day. One of the goals for NIF has been to reduce this time to less than four hours, in order to allow 700 firings a year.<ref name=performance>'' {{webarchive |url=https://web.archive.org/web/20100528023239/https://publicaffairs.llnl.gov/news/news_releases/2003/NR-03-06-01.html |date=May 28, 2010 }}'', Lawrence Livermore National Laboratory, June 5, 2003. Retrieved on May 7, 2008.</ref> | |||
==Criticisms== | |||
] designed for the NIF]] | |||
Critics point out that it appears that the primary basis for the construction of NIF is to help with the ] (in particular the secondary – or fusion – stage of hydrogen bombs, see ] for details), and since this second stage is extremely resilient, it appears there is no need for testing the second stage in the manner that NIF would. Additionally, if problems with the fusion component of bombs did develop in the future, there is doubt as to how much the information learned from NIF would be of aid in maintaining the stockpile. | |||
]–] gas or D–T ice. The capsule is held in the ] using thin plastic webbing.]] | |||
=== Other concepts === | |||
However, in 2001 it was learned that LLNL was pursuing a method to allow the use of ] and ] in experiments on NIF<ref></ref>; this would allow a direct examination of ] parameters for these materials at extremely high pressures and densities not currently allowed by subcritical experiments which compress the fissile material using conventional explosives. The decision does not appear to be finalized at this time though. | |||
NIF is also exploring new types of targets. Previous experiments generally used plastic ], typically ] (CH). NIF targets are constructed by coating a plastic form with a layer of sputtered ] or beryllium–copper alloy, and then oxidizing the plastic out of the center.<ref>{{cite journal |last1=Wilson |first1=Douglas C. |last2=Bradley |first2=Paul A. |last3=Hoffman |first3=Nelson M. |last4=Swenson |first4=Fritz J. |last5=Smitherman |first5=David P. |last6=Chrien |first6=Robert E. |last7=Margevicius |first7=Robert W. |last8=Thoma |first8=D. J. |last9=Foreman |first9=Larry R. |last10=Hoffer |first10=James K. |last11=Goldman |first11=S. Robert |last12=Caldwell |first12=Stephen E. |last13=Dittrich |first13=Thomas R. |last14=Haan |first14=Steven W. |last15=Marinak |first15=Michael M. |last16=Pollaine |first16=Stephen M. |last17=Sanchez |first17=Jorge J. |title=The development and advantages of beryllium capsules for the National Ignition Facility |journal=Physics of Plasmas |date=May 1998 |volume=5 |issue=5 |pages=1953–1959 |doi=10.1063/1.872865 |bibcode=1998PhPl....5.1953W |url=https://digital.library.unt.edu/ark:/67531/metadc694360/ |access-date=October 11, 2019 |archive-date=December 16, 2022 |archive-url=https://web.archive.org/web/20221216011808/https://digital.library.unt.edu/ark:/67531/metadc694360/ |url-status=live }}</ref><ref>{{Cite web |title=Meeting the Target Challenge |url=https://www.llnl.gov/str/JulAug07/Atherton.html |archive-url=https://web.archive.org/web/20081115130949/https://www.llnl.gov/str/JulAug07/Atherton.html |archive-date=November 15, 2008 |access-date=May 7, 2008 |publisher=Science & Technology Review}}</ref> Beryllium targets offer higher implosion efficiencies from x-ray inputs.<ref>{{Cite journal |last1=Wilson |first1=D. C. |last2=Yi |first2=S. A. |last3=Simakov |first3=A. N. |last4=Kline |first4=J. L. |last5=Kyrala |first5=G. A. |last6=Dewald |first6=E. L. |last7=Tommasini |first7=R. |last8=Ralph |first8=J. E. |last9=Olson |first9=R. E. |last10=Strozzi |first10=D. J. |last11=Celliers |first11=P. M. |last12=Schneider |first12=M. B. |last13=MacPhee |first13=A. G. |last14=Zylstra |first14=A. B. |last15=Callahan |first15=D. A. |title=X-Ray Drive of Beryllium Capsule Implosions at the National Ignition Facility |journal=Journal of Physics: Conference Series |volume=717 |doi=10.1088/1742-6596/717/1/012058 |issn=1742-6588 |last16=Hurricane |first16=O. A. |last17=Milovich |first17=J. L. |last18=Hinkel |first18=D. E. |last19=Rygg |first19=J. R. |last20=Rinderknecht |first20=H. G. |last21=Sio |first21=H. |last22=Perry |first22=T. S. |last23=Batha |first23=S.|year=2016 |issue=1 |page=012058 |bibcode=2016JPhCS.717a2058W |s2cid=114667921 |doi-access=free }}</ref> | |||
Although NIF was primarily designed as an indirect drive device, the energy in the laser as of 2008 was high enough to be used as a direct drive system, where the laser shines directly on the target without conversion to x-rays. The power delivered by NIF UV rays was estimated to be more than enough to cause ignition, allowing ] of about 40x, somewhat higher than the indirect drive system.<ref>S. V. Weber et al., '' {{Webarchive |url=https://web.archive.org/web/20221213185556/https://flux.aps.org/meetings/YR9596/BAPSDPP95/abs/S6P06.html |date=December 13, 2022 }}'', MIXED session, November 8. Retrieved on May 7, 2008.</ref> | |||
<gallery> | |||
Image:NIF_target_chamber.jpg|A construction worker inside NIF's 10 meter target chamber. Almost all of the engineering on the NIF laser is on an enormous scale. | |||
As of 2005, scaled implosions on the OMEGA laser and computer simulations showed NIF to be capable of ignition using a polar direct drive (PDD) configuration where the target was irradiated directly by the laser only from the top and bottom, without changes to the NIF beamline layout.<ref name=pdd>Yaakobi, B.; R. L. McCrory, S. Skupsky, et al. '''', LLE Review, Vol 104, September 2005, pp. 186–8. Retrieved on May 7, 2008 {{webarchive |url=https://web.archive.org/web/20070102194728/http://www.lle.rochester.edu/pub/review/v104/104_03Polar.pdf |date=January 2, 2007 }}</ref> <!-- In this configuration the target suffers either a "pancake" or "cigar" ] on implosion, reducing the maximum core temperature.{{cn|date=December 2022}} --> | |||
image:nif_flashlamps.jpg|The flashlamps used to pump the main amplifiers are the largest ever in commercial production. | |||
Image:Laser glass slabs.jpg|The glass slabs used in the amplifiers are likewise much larger than previous lasers. | |||
As of 2005, other targets, called saturn targets, were specifically designed to reduce the anisotropy and improve the implosion.<ref>True, M. A.; J. R. Albritton, and E. A. Williams, ", LLE Review, Vol. 102, January–March 2005, pp. 61–6. Retrieved on May 7, 2008. {{webarchive |url=https://web.archive.org/web/20080829235200/http://www.lle.rochester.edu/pub/review/v102/102_01Saturn.pdf |date=August 29, 2008 }}</ref> They feature a small plastic ring around the "equator" of the target, which becomes a plasma when hit by the laser. Some of the laser light is refracted through this plasma back towards the equator of the target, evening out the heating. NIF ignition with gains of just over 35 times are thought to be possible, producing results almost as good as the fully symmetric direct drive approach.<ref name="pdd" /> | |||
Image:KDP crystal.jpg|A large ] crystal grown at ] to be cut into slices and used on NIF for ] from the IR fundamental line at 1054 nm to UV at 351 nm. | |||
== History == | |||
=== Impetus, 1957 === | |||
The history of ICF at ] in ], started with physicist ], who started considering the problem after a 1957 meeting arranged by ] there. During these meetings, the idea later known as ] emerged. PACER envisioned the explosion of small ]s in large caverns to generate steam that would be converted into electrical power. After identifying problems with this approach, Nuckolls wondered how small a bomb could be made that would still generate net positive power.<ref name="EarlyNuckolls" /> | |||
A typical hydrogen bomb has two parts: a plutonium-based fission bomb known as the ''primary'', and a cylindrical arrangement of fusion fuels known as the ''secondary''. The primary releases x-rays, which are trapped within the bomb casing. They heat and compress the secondary until it ignites. The secondary consists of ] (LiD) fuel, which requires an external neutron source. This is normally in the form of a small plutonium "spark plug" in the center of the fuel. Nuckolls's idea was to explore how small the secondary could be made, and what effects this would have on the energy needed from the primary to cause ignition. The simplest change is to replace the LiD fuel with DT gas, removing the need for the spark plug. This allows secondaries of any size – as the secondary shrinks, so does the amount of energy needed for ignition. At the milligram level, the energy levels started to approach those available through several known devices.<ref name=EarlyNuckolls>{{cite web|first=John |last=Nuckolls|url=http://www.osti.gov/bridge/servlets/purl/658936-fpqpjO/webviewable/658936.pdf |title=Early Steps Toward Inertial Fusion Energy (IFE) |archive-url=https://web.archive.org/web/20221213185556/https://www.osti.gov/biblio/658936 |archive-date=December 13, 2022 |publisher=LLNL |date=June 12, 1998|doi=10.2172/658936 }}</ref> | |||
By the early 1960s, Nuckolls and several other weapons designers had developed ICF's outlines. The DT fuel would be placed in a small capsule, designed to rapidly ablate when heated and thereby maximize compression and shock wave formation. This capsule would be placed within an engineered shell, the hohlraum, which acts like the bomb casing. The hohlraum did not have to be heated by x-rays; any source of energy could be used as long as it delivered enough energy to heat the hohlraum and produce x-rays. Ideally the energy source would be located some distance away, to mechanically isolate both ends of the reaction. A small atomic bomb could be used as the energy source, as in a hydrogen bomb, but ideally smaller energy sources would be used. Using computer simulations, the teams estimated that about 5 MJ of energy would be needed from the primary, generating a 1 MJ beam.<ref name="EarlyNuckolls" /> To put this in perspective, a small (0.5 kt ) fission primary releases 2 TJ.<ref>{{cite web|url=http://www.unitjuggler.com/convert-energy-from-kT-to-MJ.html |title=Convert kilotons, to megajoules|archive-url=https://web.archive.org/web/20221213185558/https://www.unitjuggler.com/convert-energy-from-kT-to-MJ.html |archive-date=December 13, 2022 |publisher=Unit Juggler}}</ref><ref>{{cite journal|display-authors=etal |author=Nuckolls |url=http://www.nature.com/nature/journal/v239/n5368/pdf/239139a0.pdf |title=Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications|archive-url=https://web.archive.org/web/20110922173009/http://www.nature.com/nature/journal/v239/n5368/pdf/239139a0.pdf |archive-date=September 22, 2011 |journal=Nature |volume= 239|year= 1972 |issue=5368 |page= 129|doi=10.1038/239139a0 |bibcode=1972Natur.239..139N |s2cid=45684425 }}</ref><ref>{{cite web |first=John |last=Lindl |url=http://www.osti.gov/bridge/servlets/purl/10126383-6NAuBK/native/10126383.pdf | |||
|title=The Edward Teller Medal Lecture: The Evolution Toward Indirect Drive and Two Decades of Progress Toward ICF Ignition and Burn|archive-url=https://web.archive.org/web/20221213185556/https://www.osti.gov/biblio/10126383 |archive-date=December 13, 2022 |publisher=11th International Workshop on Laser Interaction and Related Plasma Phenomena |date=December 1994|access-date= May 7, 2008}}</ref> | |||
=== ICF program, 1970s === | |||
While Nuckolls and LLNL were working on hohlraum-based concepts, ] physicist ] was independently working on direct drive. In the early 1970s, Brueckner formed ] to commercialize this concept. This sparked an intense rivalry between KMS and the weapons labs. Formerly ignored, ICF became a hot topic and most of the labs started ICF work.<ref name="EarlyNuckolls" /> LLNL decided to concentrate on glass lasers, while other facilities studied gas lasers using carbon dioxide (e.g. ANTARES, ]) or KrF (e.g. ], ]).<ref>{{cite journal|url=https://lasers.llnl.gov/multimedia/publications/pdfs/etr/1985_02_1.pdf|title=Nova Review|journal=Energy and Technology Review|access-date=December 15, 2022|archive-date=December 20, 2022|archive-url=https://web.archive.org/web/20221220003519/https://lasers.llnl.gov/multimedia/publications/pdfs/etr/1985_02_1.pdf|url-status=live}}</ref> | |||
Throughout these early stages, much of the understanding of the fusion process was the result of computer simulations, primarily ]. LASNEX simplified the reaction to a 2-dimensional approximation, which was all that was possible with the available computing power. LASNEX estimated that laser drivers in the kJ range could reach low gain, which was just within the state of the art.<ref name="EarlyNuckolls" /> This led to the ] project which was completed in 1977. Shiva fell far short of its goals. The densities reached were thousands of times smaller than predicted. This was traced to issues with the way the laser delivered heat to the target. Most of its energy energized electrons rather than the entire fuel mass. Further experiments and simulations demonstrated that this process could be dramatically improved by using shorter wavelengths.<ref>{{Cite web|url=https://www.llnl.gov/archives/1970s/shiva-laser-system|title=Shiva Laser System|website=www.llnl.gov|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215014243/https://www.llnl.gov/archives/1970s/shiva-laser-system|url-status=live}}</ref> | |||
Further upgrades to the simulation programs, accounting for these effects, predicted that a different design would reach ignition. This system took the form of the 20-beam 200 kJ ]. During the construction phase, Nuckolls found an error in his calculations, and an October 1979 review chaired by former LLNL director ] confirmed that Nova would not reach ignition. It was modified into a smaller 10-beam design that converted the light to 351 nm and increase coupling efficiency.<ref name=peer>{{cite tech report |first1=Matthew |last1=McKinzie |first2=Christopher |last2=Paine |url=http://www.nrdc.org/nuclear/nif2/findings.asp |title=When Peer Review Fails |publisher=NDRC}}</ref> Nova was able to deliver about 30 kJ of UV laser energy, about half of what was expected, primarily due to optical damage to the final focusing optics. Even at those levels, it was clear that the predictions for fusion production were wrong; even at the limited powers available, fusion yields were far below predictions.{{cn|date=January 2023}} | |||
=== Halite and Centurion, 1978 === | |||
Each experiment showed that the energy needed to reach ignition continued to be underestimated. The ] (DOE) decided that direct experimentation was the best way to settle the issue, and in 1978 they started a series of underground experiments at the ] that used small nuclear bombs to illuminate ICF targets. The tests were known as Halite (LLNL) and Centurion (LANL).<ref name="auto">{{Cite book|chapter-url=https://www.sciencedirect.com/science/article/pii/B978012384656300012X|title=Fusion|first1=Garry|last1=McCracken|first2=Peter|last2=Stott|chapter=Chapter 12 – Large Inertial-Confinement Systems|editor-first1=Garry|editor-last1=McCracken|editor-first2=Peter|editor-last2=Stott|date=January 1, 2013|publisher=Academic Press|pages=149–164|doi=10.1016/B978-0-12-384656-3.00012-X|isbn=978-0-12-384656-3|via=ScienceDirect|edition=Second|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215014358/https://www.sciencedirect.com/science/article/pii/B978012384656300012X|url-status=live}}</ref> | |||
The basic concept behind the tests had been developed in the 1960s as a way to develop ] warheads. It was found that bombs that exploded outside the atmosphere gave off bursts of X-rays that could damage an enemy warhead at long range. To test the effectiveness of this system, and to develop countermeasures to protect US warheads, the ] (now the Defense Threat Reduction Agency) developed a system that placed the targets at the end of long tunnels behind fast-shutting doors. The doors were timed to shut in the brief period between the arrival of the X-rays and the subsequent blast. This saved the ] (RV) from blast damage and allowed them to be inspected.<ref name="auto" /> | |||
ICF tests used the same system, replacing the RVs by hohlraums. Each test simultaneously illuminated many targets, each at a different distance from the bomb to test the effect of varying of illumination. Another question was how large the fuel assembly had to be in order for the fuel to self-heat from the fusion reactions and thus reach ignition. Initial data were available by mid-1984, and the testing ceased in 1988. Ignition was achieved for the first time during these tests. The amount of energy and the size of the fuel targets needed to reach ignition was far higher than predicted.<ref name=secretadvance>{{cite news |title=Secret Advance in Nuclear Fusion Spurs a Dispute Among Scientists |first=William |last=Broad |date=March 21, 1988 |newspaper=New York Times |url=https://www.nytimes.com/1988/03/21/us/secret-advance-in-nuclear-fusion-spurs-a-dispute-among-scientists.html |access-date=February 11, 2017 |archive-date=March 11, 2017 |archive-url=https://web.archive.org/web/20170311195023/http://www.nytimes.com/1988/03/21/us/secret-advance-in-nuclear-fusion-spurs-a-dispute-among-scientists.html |url-status=live }}</ref> During this same period, experiments began on Nova using similar targets to understand their behavior under laser illumination, allowing direct comparison against the bomb tests.<ref>John Lindl, "A strategy for determining the driver requirements for high gain ICF implosions utilizing hydrodynamically equivalent capsules on Nova laser", Laser Annual Program Report, 1981, Lawrence Livermore Laboratory, Livermore, CA, UCRL-50055-80/81, pp.2-29-2-57 (unpublished)</ref> | |||
This data suggested that about 10 MJ of X-ray energy would be needed to reach ignition, far beyond what had earlier been calculated.<ref name="secretadvance" /><ref>{{cite journal|first1=John |last1=Lindl |first2=Rober |last2=McCrory |first3=Michael |last3=Campbell |url=http://www.physics.utoronto.ca/~phy189h1/Ignition%20and%20Inertial%20Confinement%20Fusion.pdf |title=Progress Toward Ignition and Burn Propagation in Inertial Confinement Fusion|archive-url=https://web.archive.org/web/20130731181633/http://www.physics.utoronto.ca/~phy189h1/Ignition%20and%20Inertial%20Confinement%20Fusion.pdf |archive-date=July 31, 2013 |journal=Physics Today|date=September 1992 |volume=45 |issue=9 |pages= 32–40|doi=10.1063/1.881318 |bibcode=1992PhT....45i..32L }}</ref><ref>{{cite web |url=http://classic.the-scientist.com/?articles.view/articleNo/10455/ |archive-url=https://archive.today/20150508183810/http://classic.the-scientist.com/?articles.view/articleNo/10455/ |url-status=dead |archive-date=May 8, 2015 |title=Infighting Among Rival Theorists Imperils 'Hot' Fusion Lab Plan |website=The Scientist }}</ref><ref>{{cite journal|first1=Phillip |last1=Schewe |first2= Ben |last2=Stein |url=http://nuclearweaponarchive.org/News/Lindl.txt |title=Inertial Confinement Fusion (ICF) Article Announcement|journal=Physics News|date=October 25, 1995}}</ref> If those X-rays are created by beaming an IR laser to a hohlraum, as in Nova or NIF, then dramatically more laser energy would be required, on the order of 100 MJ.<ref name="secretadvance" /> | |||
This triggered a debate in the ICF community.<ref name="secretadvance" /> One group suggested an attempt to build a laser of this power; ] and Claude Phipps designed a new type of ] pumped by high-energy ]s and reach the 100 MJ threshold. Others used the same data and new versions of their computer simulations to suggest that careful shaping of the laser pulse and more beams spread more evenly could achieve ignition with a laser powered between 5 and 10 MJ.<ref>{{cite journal |url=http://www.osti.gov/bridge/servlets/purl/6686429-47queD/6686429.pdf |title=Information Bridge: DOE Scientific and Technical Information – Sponsored by OSTI<!-- Bot generated title --> |date=September 28, 1988 |website=osti.gov |last1=Storm |first1=E. |access-date=October 18, 2012 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082144/http://www.osti.gov/bridge/servlets/purl/6686429-47queD/6686429.pdf |url-status=live }}</ref><ref>John Lindl, Development of the Indirect-Drive Approach to Inertial Confinement Fusion and the Target Physics Basis for Ignition and Gain, Physics of Plasmas Vol. 2, No. 11, November 1995; pp. 3933–4024</ref> | |||
These results prompted the DOE to request a custom military ICF facility named the "Laboratory Microfusion Facility" (LMF). LMF would use a driver on the order of 10 MJ, delivering fusion yields of between 100 and 1,000 MJ. A 1989–1990 review of this concept by the ] suggested that LMF was too ambitious, and that fundamental physics needed to be further explored. They recommended further experiments before attempting to move to a 10 MJ system. Nevertheless, the authors noted, "Indeed, if it did turn out that a 100 MJ driver were required for ignition and gain, one would have to rethink the entire approach to, and rationale for, ICF".<ref>{{cite journal | url=https://link.springer.com/content/pdf/10.1007/BF01050621.pdf | doi=10.1007/BF01050621 | title=Review of the department of energy's inertial confinement fusion program | year=1991 | last1=Koonin | first1=Steven E. | last2=Carrier | first2=George F. | last3=Christy | first3=Robert F. | last4=Conn | first4=Robert W. | last5=Davidson | first5=Ronald C. | last6=Dawson | first6=John M. | last7=Demaria | first7=Anthony J. | last8=Doty | first8=Paul M. | last9=Happer | first9=William | last10=Kulcinski | first10=Gerald L. | last11=Longmire | first11=Conrad L. | last12=Powell | first12=James R. | last13=Rosenbluth | first13=Marshall N. | last14=Ruina | first14=Jack P. | last15=Sproull | first15=Robert L. | last16=Tigner | first16=Maury | last17=Wagner | first17=Richard L. | journal=Journal of Fusion Energy | volume=10 | issue=2 | pages=157–172 | bibcode=1991JFuE...10..157K | s2cid=122974976 | access-date=December 15, 2022 | archive-date=June 8, 2024 | archive-url=https://web.archive.org/web/20240608082134/https://link.springer.com/content/pdf/10.1007/BF01050621.pdf | url-status=live }}</ref> | |||
=== Laboratory Microfusion Facility and Nova Upgrade, 1990 === | |||
As of 1992, the Laboratory Microfusion Facility was estimated to cost about $1 billion.<ref name=upgrade>''Nova Upgrade – A Proposed ICF Facility to Demonstrate Ignition and Gain'', Lawrence Livermore National Laboratory ICF Program, July 1992 https://ui.adsabs.harvard.edu/abs/1992nupi.rept....../abstract {{Webarchive|url=https://web.archive.org/web/20221215015243/https://ui.adsabs.harvard.edu/abs/1992nupi.rept....../abstract |date=December 15, 2022 }}</ref> LLNL initially submitted a design with a 5 MJ 350 nm (UV) driver that would be able to reach about 200 MJ yield, which was enough to attain the majority of the LMF goals.That program was estimated to cost about $600 million FY 1989 dollars. An additional $250 million would pay to upgrade it to a full 1,000 MJ. The total would surpass $1 billion to meet all of the goals requested by the DOE.<ref name="upgrade" /> <!-- Other labs proposed LMF designs using other technologies.{{cn|date=December 2022}} --> | |||
The NAS review led to a reevaluation of these plans, and in July 1990, LLNL responded with the Nova Upgrade, which would reuse most of Nova, along with the adjacent Shiva facility. The resulting system would be much lower power than the LMF concept, with a driver of about 1 MJ.<ref>Tobin, M.T et al., '' '', Fusion Engineering, 1991, pg. 650–655. Retrieved on May 7, 2008.</ref> The new design included features that advanced the state of the art in the driver section, including multi-pass in the main amplifiers, and 18 beamlines (up from 10) that were split into 288 "beamlets" as they entered the target area. The plans called for the installation of two main banks of beamlines, one in the existing Nova beamline room, and the other in the older Shiva building next door, extending through its laser bay and target area into an upgraded Nova target area. The lasers would deliver about 500 TW in a 4 ns pulse. The upgrades were expected to produce fusion yields of between 2 and 10 MJ. The initial estimates from 1992 estimated construction costs around $400 million, with construction taking place from 1995 to 1999.<ref name="upgrade" /> | |||
=== NIF, 1994 === | |||
Throughout this period, the ending of the ] led to dramatic changes in defense funding and priorities. The political support for nuclear weapons declined and arms agreements led to a reduction in warhead count and less design work. The US was faced with the prospect of losing a generation of nuclear weapon designers able to maintain existing stockpiles, or design new weapons.<ref>William Broad, '' {{Webarchive |url=https://web.archive.org/web/20221213185557/https://www.nytimes.com/1994/06/21/science/vast-laser-plan-would-further-fusion-and-keep-bomb-experts.html |date=December 13, 2022 }}'', New York Times, June 21, 1994. Retrieved on May 7, 2008.</ref> At the same time, the ] (CTBT) was signed in 1996, which would ban all ] testing and made the development of newer generations of nuclear weapons more difficult. | |||
].]] | |||
Out of these changes came the ] (SSMP), which, among other things, included funds for the development of methods to design and build nuclear weapons without having to test them explosively. In a series of meetings that started in 1995, an agreement formed between the labs to divide up SSMP efforts. An important part of this would be confirmation of computer models using low-yield ICF experiments. The Nova Upgrade was too small to use for these experiments.<ref>Letter from Charles Curtis, Undersecretary of Energy, June 15, 1995</ref>{{efn|It is not clearly stated why Nova Upgrade would be too small for SSMP, no reason is given in the available resources.}} A redesign matured into NIF in 1994. The estimated cost of the project remained almost $1 billion, with completion in 2002.<ref>{{Cite web|url=https://www.laserfocusworld.com/test-measurement/research/article/16551113/photonic-frontiers-the-national-ignition-facility-nif-is-up-and-running-at-last|title=Photonic Frontiers: The National Ignition Facility: NIF is up and running at last|website=www.laserfocusworld.com|date=November 2009|access-date=December 15, 2022|archive-date=June 8, 2024|archive-url=https://web.archive.org/web/20240608082136/https://www.laserfocusworld.com/test-measurement/research/article/16551113/photonic-frontiers-the-national-ignition-facility-nif-is-up-and-running-at-last|url-status=live}}</ref> | |||
In spite of the agreement, the large project cost combined with the ending of similar projects at other labs resulted in critical comments by scientists at other labs, ] in particular. In May 1997, Sandia fusion scientist Rick Spielman publicly stated that NIF had "virtually no internal peer review on the technical issues" and that "Livermore essentially picked the panel to review themselves".<ref>"Livermore's costly fusion laser won't fly, scientists say", Albuquerque Tribune, May 29, 1997, p. 1</ref> A retired Sandia manager, Bob Puerifoy, was even more blunt than Spielman: "NIF is worthless ... it can't be used to maintain the stockpile, period".<ref>L. Spohn, "NIF opponents to cite criticism of laser in court battle", Albuquerque Tribune, June 13, 1997, p. A15.</ref> ], one of the original developers of the ICF concept at LLNL, was also highly critical. He stated in 1997 that its primary purpose was to "recruit and maintain a staff of theorists and experimentalists" and that while some of the experimental data would prove useful for weapons design, differences in the experimental setup limit their relevance. "Some of the physics is the same; but the details, 'wherein the devil lies,' are quite different. It would therefore also be wrong to assume that NIF will be able to support for the long term a staff of weapons designers and engineers with detailed design competence comparable to that of those now working at the weapons design laboratories."<ref>{{cite journal |journal=Nature |date=April 17, 1997 |volume=386 |first=Ray |last=Kidder |title=Problems with stockpile stewardship |issue=6626 |pages=645–647 |doi=10.1038/386645a0 |bibcode=1997Natur.386..645K |s2cid=4268081 |url=http://web.mit.edu/sts/SSBS/kidder.html |archive-url=https://web.archive.org/web/20040923102841/http://web.mit.edu/sts/SSBS/kidder.html |archive-date=September 23, 2004 }}</ref> | |||
In 1997, Victor Reis, assistant secretary for Defense Programs within DOE and SSMP chief architect defended the program telling the ] that NIF was "designed to produce, for the first time in a laboratory setting, conditions of temperature and density of matter close to those that occur in the detonation of nuclear weapons. The ability to study the behavior of matter and the transfer of energy and radiation under these conditions is key to understanding the basic physics of nuclear weapons and predicting their performance without underground nuclear testing."<ref>Statement of Dr. Victor Reis, Assistant Secretary for Defense Programs, Department of Energy, before the Senate Armed Services Committee, March 19, 1997 (retrieved July 13, 2012, from http://www.lanl.gov/orgs/pa/Director/reisSASC97.html {{Webarchive |url=https://web.archive.org/web/20050104210728/http://www.lanl.gov/orgs/pa/Director/reisSASC97.html |date=January 4, 2005 }} )</ref> In 1998, two JASON panels, composed of scientific and technical experts, stated that NIF is the most scientifically valuable of all programs proposed for science-based stockpile stewardship.<ref>{{cite web |url=http://www.armed-services.senate.gov/statemnt/980326fp.htm |title=Statement of Federico Peña, Secretary, US Dept of Energy, before the Committee on Armed Services, United States Senate |date=March 26, 1998 |access-date=July 13, 2012 |archive-url=https://web.archive.org/web/20110205200200/http://armed-services.senate.gov/statemnt/980326fp.htm |archive-date=February 5, 2011}}</ref> | |||
Despite the initial criticism, Sandia, as well as Los Alamos, supported the development of many NIF technologies,<ref>{{cite report |url=http://www.osti.gov/bridge/purl.cover.jsp?purl=/274120-bKjglv/webviewable/274120.pdf |title=Information Bridge: DOE Scientific and Technical Information – Sponsored by OSTI |publisher=Osti.gov |date=August 31, 2012 |access-date=October 8, 2012 |last1=Boyes |first1=J. |last2=Boyer |first2=W. |last3=Chael |first3=J. |last4=Cook |first4=D. |last5=Cook |first5=W. |last6=Downey |first6=T. |last7=Hands |first7=J. |last8=Harjes |first8=C. |last9=Leeper |first9=R. |last10=McKay |first10=P. |last11=Micano |first11=P. |last12=Olson |first12=R. |last13=Porter |first13=J. |last14=Quintenz |first14=J. |last15=Roberts |first15=V. |last16=Savage |first16=M. |last17=Simpson |first17=W. |last18=Seth |first18=A. |last19=Smith |first19=R. |last20=Wavrik |first20=M. |last21=Wilson |first21=M. |archive-date=July 31, 2013 |archive-url=https://web.archive.org/web/20130731202631/http://www.osti.gov/bridge/purl.cover.jsp?purl=/274120-bKjglv/webviewable/274120.pdf |url-status=live }}</ref> and both laboratories later{{when|date=December 2022}} became partners with NIF in the National Ignition Campaign.<ref>{{cite web |url=https://lasers.llnl.gov/programs/nic/participants.php |title=National Ignition Campaign: Participants, NIF & Photon Science |publisher=Lasers.llnl.gov |access-date=October 8, 2012 |archive-url=https://web.archive.org/web/20121017203631/https://lasers.llnl.gov/programs/nic/participants.php |archive-date=October 17, 2012}}</ref> | |||
=== Construction of first unit, 1994–1998 === | |||
] | |||
] | |||
Work on the NIF started with a single beamline demonstrator, Beamlet. Beamlet successfully operated between 1994 and 1997. It was then sent to ] as a light source in their ]. A full-sized demonstrator then followed, in AMPLAB, which started operations in 1997.<ref>J. A. Horvath, '' {{Webarchive |url=https://web.archive.org/web/20150908212244/https://e-reports-ext.llnl.gov/pdf/234367.pdf |date=September 8, 2015 }}'', Third Annual International Conference on Solid State Lasers for Application (SSLA) to Inertial Confinement Fusion (ICF), July 16, 1998</ref> The official groundbreaking on the main NIF site was on May 29, 1997.<ref>{{cite web |url=https://lasers.llnl.gov/multimedia/photo_gallery/building_nif/?id=1&category=building_nif |title=Multimedia: Photo Gallery, NIF & Photon Science |publisher=Lasers.llnl.gov |date=May 29, 1997 |access-date=October 8, 2012 |archive-url=https://web.archive.org/web/20120724042234/https://lasers.llnl.gov/multimedia/photo_gallery/building_nif/?id=1&category=building_nif |archive-date=July 24, 2012}}</ref> | |||
At the time, the DOE was estimating that the NIF would cost approximately $1.1 billion and another $1 billion for related research, and would be complete as early as 2002.<ref name=GAO1>'''', GAO, August 2000</ref> Later in 1997 the DOE approved an additional $100 million in funding and pushed the operational date back to 2004. As late as 1998 LLNL's public documents stated the overall price was $1.2 billion, with the first eight lasers coming online in 2001 and full completion in 2003.<ref>{{Cite journal|first1=Howard T. |last1=Powell |first2=Richard H. |last2=Sawicki |title= Keeping Laser Development on Target for the National Ignition Facility|date= March 1998 |url=https://str.llnl.gov/ |access-date=October 9, 2023|archive-url=https://web.archive.org/web/20100528222944/https://www.llnl.gov/str//Powell.html |archive-date=May 28, 2010 |journal=S&TR}}</ref> | |||
The facility's physical scale alone made the construction project challenging. By the time the "conventional facility" (the shell for the laser) was complete in 2001, more than 210,000 cubic yards of soil had been excavated, more than 73,000 cubic yards of concrete had been poured, 7,600 tons of reinforcing steel rebar had been placed, and more than 5,000 tons of structural steel had been erected. To isolate the laser system from vibration, the foundation of each laser bay was made independent of the rest of the structure. Three-foot-thick, 420-foot-long and 80-foot-wide slabs required continuous concrete pours to achieve their specifications.<ref name="LLNL newsline">{{cite web |url=https://newsline.llnl.gov/employee/articles/2001/10-26-01newsline.pdf |title=NIF conventional facility complete |work=Newsline |publisher=LLNL |date=October 26, 2001 |access-date=September 6, 2012 |archive-url=https://web.archive.org/web/20120726024319/https://newsline.llnl.gov/employee/articles/2001/10-26-01newsline.pdf |archive-date=July 26, 2012}}</ref> | |||
In November 1997, an ] storm dumped two inches of rain in two hours, flooding the NIF site with 200,000 gallons of water just three days before the scheduled foundation pour. The earth was so soaked that the framing for the retaining wall sank six inches, forcing the crew to disassemble and reassemble it.<ref name="LLNL newsline" /> Construction was halted in December 1997, when 16,000-year-old ] bones were discovered. Paleontologists were called in to remove and preserve the bones, delaying construction by four days.<ref>{{cite web |url=https://lasers.llnl.gov/education/fusion_fun/niffy.php |title=Fusion Fun: NIFFY, NIF & Photon Science |publisher=Lasers.llnl.gov |access-date=October 8, 2012 |archive-url=https://web.archive.org/web/20130125052443/https://lasers.llnl.gov/education/fusion_fun/niffy.php |archive-date=January 25, 2013}}</ref> | |||
A variety of research and development, technology and engineering challenges arose, such as creating an optics fabrication capability to supply the laser glass for NIF's 7,500 meter-sized optics. State-of-the-art optics measurement, coating and finishing techniques were developed to withstand NIF's high-energy lasers, as were methods for amplifying the laser beams to the needed energy levels.<ref>{{cite web |last=Osolin |first=Charles |url=http://www.innovation-america.org/harnessing-power-light |title=Harnessing the Power of Light |publisher=Innovation America |access-date=October 8, 2012 |archive-date=September 8, 2015 |archive-url=https://web.archive.org/web/20150908212244/http://www.innovation-america.org/harnessing-power-light |url-status=live }}</ref> Continuous-pour glass, rapid-growth crystals, innovative optical switches, and deformable mirrors were among NIF's technology innovations developed.<ref>{{cite web |url=https://lasers.llnl.gov/about/nif/seven_wonders.php |title=National Ignition Facility: The Seven Wonders of NIF, NIF & Photon Science |publisher=Lasers.llnl.gov |access-date=October 8, 2012 |archive-url=https://web.archive.org/web/20121017204200/https://lasers.llnl.gov/about/nif/seven_wonders.php |archive-date=October 17, 2012}}</ref> | |||
Sandia, with extensive experience in pulsed power delivery, designed the capacitor banks used to feed the flashlamps, completing the first unit in October 1998. To everyone's surprise, the Pulsed Power Conditioning Modules (PCMs) suffered capacitor failures that led to explosions. This required a redesign of the module to contain the debris, but since the concrete had already been poured, this left the new modules so tightly packed that in-place maintenance was impossible. Another redesign followed, this time allowing the modules to be removed from the bays for servicing.<ref name="peer" /> Continuing problems further delayed operations, and in September 1999, an updated DOE report stated that NIF required up to $350 million more and completion occur only in 2006.<ref name="GAO1" /> | |||
=== Re-baseline and GAO report, 1999–2000 === | |||
] | |||
Throughout this period the problems with NIF were not reported up the management chain. In 1999 then ] ] reported to Congress that NIF was on time and budget, as project leaders had reported. In August that year it was revealed that neither claim was close to the truth.<ref name=nyt>James Glanz, '' {{Webarchive |url=https://web.archive.org/web/20160603090058/http://www.nytimes.com/library/national/science/081900sci-laser-missiles.html |date=June 3, 2016 }}'', New York Times, August 19, 2000. Retrieved on May 7, 2008.</ref> As the ] (GAO) would later note, "Furthermore, the Laboratory's former laser director, who oversaw NIF and all other laser activities, assured Laboratory managers, DOE, the university, and the Congress that the NIF project was adequately funded and staffed and was continuing on cost and schedule, even while he was briefed on clear and growing evidence that NIF had serious problems".<ref name="GAO1" /> A DOE Task Force reported to Richardson in January 2000 that "organizations of the NIF project failed to implement program and project management procedures and processes commensurate with a major research and development project... ...no one gets a passing grade on NIF Management: not the DOE's office of Defense Programs, not the Lawrence Livermore National Laboratory and not the University of California".<ref>'''', Secretary of Energy Advisory Board, January 10, 2000. Retrieved on May 7, 2008. {{webarchive |url=https://web.archive.org/web/20070629215119/http://www.seab.energy.gov/publications/nif_rpt.pdf |date=June 29, 2007 }}</ref> | |||
Given the budget problems, the ] requested an independent GAO review. They returned a critical report in August 2000 estimating that the cost was likely to be $3.9 billion, including R&D, and that the facility was unlikely to be completed anywhere near on time.<ref name="GAO1" /><ref name=fas101>'''', FYI, American Institute of Physics, Number 101: August 30, 2000. Retrieved on May 7, 2008.</ref> The report noted management problems for the overruns, and criticized the program for failing to budget money for target fabrication, including it in operational costs instead of development.<ref name="nyt" /> | |||
In 2000, the DOE began a comprehensive "rebaseline review" because of the technical delays and project management issues, and adjusted the schedule and budget accordingly. ], National Nuclear Security Administrator, stated "We have prepared a detailed bottom-up cost and schedule to complete the NIF project... The independent review supports our position that the NIF management team has made significant progress and resolved earlier problems".<ref>Ian Hoffman, '' {{Webarchive |url=https://web.archive.org/web/20110708050138/http://lanl-the-rest-of-the-story.blogspot.com/2007/06/nuclear-testing-gear-in-doubt-livermore.html |date=July 8, 2011 }}'', MediaNews Group,</ref> The report revised their budget estimate to $2.25 billion, not including related R&D which pushed it to $3.3 billion total, and pushed back the completion date to 2006 with the first lines coming online in 2004.<ref name=fas65>'''', FYI: The API Bulletin of Science Policy News, American Institute of Physics. Retrieved on May 7, 2008.</ref><ref>'''', FYI, American Institute of Physics, Number 65, June 15, 2000. Retrieved on May 7, 2008.</ref> A follow-up report the next year pushed the budget to $4.2 billion, and the completion date to 2008.] | |||
The project got a new management team<ref>''LLNL Management Changes'', Fusion Power Associates, | |||
September 10, 1999, http://aries.ucsd.edu/FPA/ARC99/fpn99-43.shtml {{Webarchive |url=https://web.archive.org/web/20160304131237/http://aries.ucsd.edu/FPA/ARC99/fpn99-43.shtml |date=March 4, 2016 }} (retrieved July 13, 2012)</ref><ref>''Campbell Investigation Triggers Livermore Management Changes'', Fusion Power Report, Sep 1, 1999 | |||
http://www.thefreelibrary.com/Campbell+Investigation+Triggers+Livermore+Management+Changes.-a063375944 {{Webarchive |url=https://web.archive.org/web/20160305134849/http://www.thefreelibrary.com/Campbell+Investigation+Triggers+Livermore+Management+Changes.-a063375944 |date=March 5, 2016 }} (retrieved July 13, 2012)</ref> in September 1999, headed by ], who was named acting associate director for lasers. ], former head of the ] (AVLIS) program at LLNL, became NIF project manager. Thereafter, NIF management received many positive reviews and the project met the budgets and schedules approved by Congress. In October 2010, the project was named "Project of the Year" by the ], which cited NIF as a "stellar example of how properly applied project management excellence can bring together global teams to deliver a project of this scale and importance efficiently."<ref>{{cite web |url=https://www.llnl.gov/news/newsreleases/2010/Oct/NR-10-10-03.html |title=National Ignition Facility wins prestigious 2010 project of the year award |author=<!--Staff writer(s); no by-line.--> |date=October 11, 2010 |website=llnl.gov |publisher=] |access-date=July 13, 2012 |archive-date=July 26, 2012 |archive-url=https://web.archive.org/web/20120726024036/https://www.llnl.gov/news/newsreleases/2010/Oct/NR-10-10-03.html }}</ref> | |||
=== Tests and construction completion, 2003–2009 === | |||
In May 2003, the NIF achieved "first light" on a bundle of four beams, producing a 10.4 kJ IR pulse in a single beamline.<ref name="performance" /> In 2005 the first eight beams produced 153 kJ of IR, eclipsing OMEGA as the planet's highest energy laser (per pulse). By January 2007 all of the LRUs in the Master Oscillator Room (MOOR) were complete and the computer room had been installed. By August 2007, 96 laser lines were completed and commissioned, and "A total infrared energy of more than 2.5 megajoules has now been fired. This is more than 40 times what the Nova laser typically operated at the time it was the world's largest laser".<ref>'' {{webarchive |url=https://web.archive.org/web/20100527234734/https://publicaffairs.llnl.gov/news/news_releases/2007/NR-07-11-05.html |date=May 27, 2010 }}'', Lawrence Livermore National Laboratory, November 21, 2007. Retrieved on May 7, 2008.</ref> | |||
In 2005, an independent review by the ] that was generally positive, concluded that "The scientific and technical challenges in such a complex activity suggest that success in the early attempts at ignition in 2010, while possible, is unlikely".<ref name=jason>'' {{Webarchive |url=https://web.archive.org/web/20090424080032/http://www.fas.org/irp/agency/dod/jason/nif.pdf |date=April 24, 2009 }}'', JASON Program, June 29, 2005</ref> On January 26, 2009, the final line replaceable unit (LRU) was installed,<ref>{{cite web |url=https://newsline.llnl.gov/_rev02/articles/2009/jan/01.30.09-nif.php |title=Last of 6,206 modules installed in NIF |last=Hirschfeld |first=Bob |publisher=Lawrence Livermore National Laboratory |date=January 30, 2009 |access-date=April 3, 2009 |archive-url=https://web.archive.org/web/20110718033618/https://newsline.llnl.gov/_rev02/articles/2009/jan/01.30.09-nif.php |archive-date=July 18, 2011}}</ref> unofficially completing construction.<ref name="complete">{{cite news |title=Project Status February 2009 |publisher=] |date=February 26, 2009 |url=https://lasers.llnl.gov/newsroom/project_status/2009/february.php |access-date=March 11, 2009 |archive-url=https://web.archive.org/web/20100528000209/https://lasers.llnl.gov/newsroom/project_status/2009/february.php |archive-date=May 28, 2010}}</ref> On February 26, 2009, NIF fired all 192 laser beams into the target chamber.<ref>{{cite web |url=https://newsline.llnl.gov/_rev02/articles/2009/mar/03.06.09-nif.php |title=NIF's future ignites with 192-beam shot |author=Seaver, Lynda |author2=Hirschfeld, Bob |publisher=Lawrence Livermore National Laboratory |date=March 6, 2009 |access-date=April 3, 2009 |archive-url=https://web.archive.org/web/20100528020137/https://newsline.llnl.gov/_rev02/articles/2009/mar/03.06.09-nif.php |archive-date=May 28, 2010}}</ref> On March 10, 2009, NIF became the first laser to break the megajoule barrier, delivering 1.1 MJ of UV light, known as 3ω (from ]), to the target chamber center in a shaped ignition pulse.<ref>{{cite web |url=https://newsline.llnl.gov/_rev02/articles/2009/mar/03.13.09-nif.php |title=NIF breaks megaJoule barrier |publisher=Lawrence Livermore National Laboratory |date=March 13, 2009 |access-date=April 3, 2009 |archive-url=https://web.archive.org/web/20100527202123/https://newsline.llnl.gov/_rev02/articles/2009/mar/03.13.09-nif.php |archive-date=May 27, 2010}}</ref> The main laser delivered 1.952 MJ of IR.<ref>{{Cite web|url=https://www.llnl.gov/news/nif-breaks-megajoule-barrier|title=NIF breaks megaJoule barrier|website=LLNL.gov|access-date=December 15, 2022|archive-date=December 15, 2022|archive-url=https://web.archive.org/web/20221215020906/https://www.llnl.gov/news/nif-breaks-megajoule-barrier|url-status=live}}</ref> | |||
=== Operations, 2009–2012 === | |||
On May 29, 2009, the NIF was dedicated in a ceremony attended by thousands.<ref name="dedication">{{cite web |date=May 29, 2009 |title=Dedication of world's largest laser marks the dawn of a new era |url=https://publicaffairs.llnl.gov/news/news_releases/2009/NR-09-05-05.html |archive-url=https://web.archive.org/web/20100527184853/https://publicaffairs.llnl.gov/news/news_releases/2009/NR-09-05-05.html |archive-date=May 27, 2010 |access-date=September 13, 2009 |publisher=]}}</ref> The first laser shots into a hohlraum target were fired in late June.<ref name="firstshots" /> | |||
==== Buildup to main experiments, 2010 ==== | |||
On January 28, 2010, NIF reported the delivery of a 669 kJ pulse to a gold ], breaking records for laser power delivery, and analysis suggested that suspected interference by generated plasma would not be a problem in igniting a fusion reaction.<ref name="Palmer">{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/8485669.stm |title=Laser fusion test results raise energy hopes |work=BBC News |author=Jason Palmer |date=January 28, 2010 |access-date=January 28, 2010 |archive-date=January 29, 2010 |archive-url=https://web.archive.org/web/20100129052407/http://news.bbc.co.uk/2/hi/science/nature/8485669.stm |url-status=live }}</ref><ref name="Seaver">{{cite web |url=https://publicaffairs.llnl.gov/news/news_releases/2010/NR-10-01-06.html |title=Initial NIF experiments meet requirements for fusion ignition |publisher=] |date=January 28, 2010 |access-date=January 28, 2010 |archive-url=https://web.archive.org/web/20100527171341/https://publicaffairs.llnl.gov/news/news_releases/2010/NR-10-01-06.html |archive-date=May 27, 2010}}</ref> Due to the size of the test hohlraums, laser/plasma interactions produced plasma-optics gratings, acting like tiny prisms, which produced symmetric X-ray drive on the capsule inside the hohlraum.<ref name="Seaver" /> | |||
After gradually altering the wavelength of the laser, scientists compressed a spherical capsule evenly and heated it to 3.3 million ]s (285 eV).<ref name="Bullis" /> The capsule contained cryogenically cooled gas, acting as a substitute for the ] and ] fuel capsules to be used later.<ref name="Seaver" /> Plasma Physics Group Leader Siegfried Glenzer said that they could maintain the precise fuel layers needed in the lab, but not yet within the laser system.<ref name="Bullis">{{cite magazine |url=http://www.technologyreview.com/blog/energy/24720/ |title=Scientists Overcome Obstacle to Fusion |last=Bullis |first=Kevin |date=January 28, 2010 |magazine=] |access-date=January 29, 2010}}</ref> | |||
As of January 2010, the NIF reached 1.8 megajoules. The target chamber then needed to be equipped with shields to block ].<ref name="Palmer" /> | |||
==== National Ignition Campaign 2010–2012 ==== | |||
] | |||
With the main construction complete, NIF started its National Ignition Campaign (NIC) to reach ignition. At the time, articles appeared in science magazines stating that ignition was imminent. '']'' opened a 2010 review article with the statement "Ignition is close now. Within a year or two..."<ref>{{cite magazine |last=Moyer |first=Michael |date=March 2010 |title=Fusion's False Dawn |url=https://www.scientificamerican.com/article/fusions-false-dawn/ |magazine=Scientific American |pages=50–57 |access-date=December 16, 2022 |archive-date=June 1, 2023 |archive-url=https://web.archive.org/web/20230601064509/https://www.scientificamerican.com/article/fusions-false-dawn/ |url-status=live }}</ref> | |||
The first test was carried out on October 8, 2010, at slightly over 1 MJ. However, problems slowed the drive toward ignition-level laser energies in the 1.4–1.5 MJ range.{{cn|date=January 2023}} | |||
One problem was the potential for damage from overheating due to a greater concentration of energy on optical components.<ref>{{cite magazine |url=http://www.scientificamerican.com/article.cfm?id=superlaser-national-ignition-facility |title=Superlaser fires a blank |author=Eugenie Samuel Reich |date=October 18, 2010 |magazine=] |access-date=October 2, 2010 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082142/https://www.scientificamerican.com/article/superlaser-national-ignition-facility/ |url-status=live }}</ref> Other issues included problems layering the fuel inside the target, and minute quantities of dust on the capsule surface.<ref name="kramerreview">{{Cite web |last=Kramer |first=David |date=April 21, 2011 |title=NIF overcomes some problems, receives mixed review from its DOE overseer |url=http://blogs.physicstoday.org/politics/2011/04/drive-for-fusion-milestone-ove.html |archive-url=https://web.archive.org/web/20110430001208/http://blogs.physicstoday.org/politics/2011/04/drive-for-fusion-milestone-ove.html |archive-date=April 30, 2011 |publisher=]}}</ref> | |||
The power level continued to increase and targets became more sophisticated. Then minute amounts of water vapor appeared in the target chamber and froze to the windows on the ends of the hohlraums, causing an asymmetric implosion. This was solved by adding a second layer of glass on either end, in effect creating a ].<ref name="kramerreview" /> | |||
Shots halted from February to April 2011, to conduct SSMP materials experiments. Then, NIF was upgraded, improving diagnostic and measurement instruments. The Advanced Radiographic Capability (ARC) system was added, which uses 4 of the NIF's 192 beams as a backlight for imaging the implosion sequence. ARC is essentially a petawatt-class laser with peak power exceeding a quadrillion (10<sup>15</sup>) watts. It is designed to produce brighter, more penetrating, higher-energy x rays. ARC became the world's highest-energy short-pulse laser, capable of creating picosecond-duration laser pulses to produce energetic x rays in the range of 50–100 keV.<ref>{{cite web |url=https://lasers.llnl.gov/news/photons-fusion/2014/may |title=Photons & Fusion Newsletter – May 2014 |author=<!--Staff writer(s); no by-line.--> |date=May 2014 |website=National Ignition Facility & Photon Science News – Archive – Photons & Fusion Newsletter |publisher=Lawrence Livermore National Laboratory |access-date=April 16, 2015 |archive-date=July 6, 2015 |archive-url=https://web.archive.org/web/20150706022251/https://lasers.llnl.gov/news/photons-fusion/2014/may |url-status=live }}</ref> | |||
NIC runs restarted in May 2011 with the goal of more precisely timing the four laser shock waves that compress the fusion target.{{cn|date=January 2023}} | |||
In January 2012, Mike Dunne, director of NIF's laser fusion energy program, predicted that ignition would be achieved at NIF by October.<ref>{{cite web |author=SPIE Europe Ltd |url=http://optics.org/news/3/1/37 |title=PW 2012: fusion laser on track for 2012 burn |publisher=Optics.org |access-date=October 8, 2012 |archive-date=March 30, 2023 |archive-url=https://web.archive.org/web/20230330114415/https://optics.org/news/3/1/37 |url-status=live }}</ref> In the same month, the NIF fired a record high 57 shots.<ref name="nature201203">{{cite journal |date=March 7, 2012 |title=Laser fusion nears crucial milestone |volume=483 |issue=7388 |pages=133–134 |author=Eric Hand |journal=Nature |doi=10.1038/483133a |pmid=22398531 |bibcode=2012Natur.483..133H |doi-access=free}}</ref> On March 15 NIF produced a laser pulse with 411 TW of peak power.<ref>{{Cite news |url=https://www.theregister.co.uk/2012/03/23/nif_laser_pulse/ |title=Record-breaking laser pulse raises fusion-power hopes |access-date=March 22, 2012 |date=March 22, 2012 |archive-date=March 23, 2012 |archive-url=https://web.archive.org/web/20120323063002/http://www.theregister.co.uk/2012/03/23/nif_laser_pulse/ |url-status=live }}</ref> On July 5, it produced a shorter pulse of 1.85 MJ and increased power of 500 TW.<ref>{{Cite web |url=https://www.foxnews.com/science/worlds-most-powerful-laser-fires-most-powerful-laser-blast-ever |title=World's most powerful laser fires most powerful laser blast ever |date=March 27, 2015 |website=Fox News |access-date=December 5, 2020 |archive-date=February 3, 2021 |archive-url=https://web.archive.org/web/20210203061935/https://www.foxnews.com/science/worlds-most-powerful-laser-fires-most-powerful-laser-blast-ever |url-status=live }}</ref> | |||
=== DOE Report, July 19, 2012 === | |||
NIC was periodically reviewed. The 6th review, was published on July 19, 2012.<ref name="Crandall">{{cite web |url=http://fire.pppl.gov/NIF_NIC_report_rev5_koonin_2012.pdf |title=External Review of the National Ignition Campaign |publisher=] |access-date=October 10, 2012 |archive-date=November 14, 2012 |archive-url=https://web.archive.org/web/20121114224543/http://fire.pppl.gov/NIF_NIC_report_rev5_koonin_2012.pdf |url-status=live }}</ref> The report praised the quality of the installation: lasers, optics, targets, diagnostics, and operations. However: | |||
:The integrated conclusion based on this extensive period of experimentation, however, is that considerable hurdles must be overcome to reach ignition or the goal of observing unequivocal alpha heating. Indeed the reviewers note that given the unknowns with the present 'semi-empirical' approach, the probability of ignition before the end of December is extremely low and even the goal of demonstrating unambiguous alpha heating is challenging.<ref name="Crandall" />{{Rp|page=2}} | |||
Further, the report expressed deep concerns that the gaps between observed performance and simulation codes implied that the current codes were of limited utility. Specifically, they found a lack of predictive ability of the radiation drive to the capsule and inadequately modeled laser–plasma interactions. Pressure was reaching only one half to one third of that required for ignition, far below the predicted values. The memo discussed the mixing of ablator material and capsule fuel likely due to hydrodynamics instabilities in the ablator's outer surface.<ref name="Crandall" /> | |||
The report suggested using a thicker ablator, although this would increase its inertia. To keep the required implosion speed, they proposed that the NIF energy be increased to 2MJ. It questioned whether or not the energy was sufficient to compress a large enough capsule to avoid the mix limit and reach ignition.{{sfn|Crandall|2012|p=5}} The report concluded that ignition within the calendar year 2012 was 'highly unlikely'.<ref name="Crandall" /> | |||
NIC officially ended on September 30, 2012. Media reports suggested that NIF would shift its focus toward materials research.<ref>{{cite journal |first=Geoff |last=Brumfiel |url=http://www.scientificamerican.com/article.cfm?id=worlds-most-powerful-laser-facility-shifts-focus-to-warheads |title=World's Most Powerful Laser Facility Shifts Focus to Warheads |journal=Scientific American |date=November 7, 2012 |access-date=November 8, 2012 |archive-date=November 8, 2012 |archive-url=https://web.archive.org/web/20121108111822/http://www.scientificamerican.com/article.cfm?id=worlds-most-powerful-laser-facility-shifts-focus-to-warheads |url-status=live }}</ref><ref>{{cite journal |journal=Nature |volume=491 |issue=7423 |page=159 |title=Editorial: Ignition switch |date=November 7, 2012 |doi=10.1038/491159a |pmid=23139940 |doi-access=free}}</ref> | |||
In 2008, LLNL began the ] program (LIFE), to explore ways to use NIF technologies as the basis for a commercial power plant design. The focus was on pure fusion devices, incorporating technologies that developed in parallel with NIF that would greatly improve the performance of the design.<ref name="endslife" /> In April 2014, LIFE ended.<ref name="endslife">{{cite journal |title=Livermore Ends LIFE |journal=Physics Today |volume=67 |issue=4 |pages=26–27 |date=April 2014 |first=David |last=Kramer |doi=10.1063/PT.3.2344 |bibcode=2014PhT....67R..26K |s2cid=178876869 }}</ref> | |||
=== Fuel gain breakeven, 2013 === | |||
A NIF fusion shot on September 27, 2013, produced more energy than was absorbed by the ] fuel.<ref name=":2">{{Cite journal |last1=Hurricane |first1=O. A. |last2=Callahan |first2=D. A. |last3=Casey |first3=D. T. |last4=Celliers |first4=P. M. |last5=Cerjan |first5=C. |last6=Dewald |first6=E. L. |last7=Dittrich |first7=T. R. |last8=Döppner |first8=T. |last9=Hinkel |first9=D. E. |last10=Hopkins |first10=L. F. Berzak |last11=Kline |first11=J. L. |last12=Le Pape |first12=S. |last13=Ma |first13=T. |last14=MacPhee |first14=A. G. |last15=Milovich |first15=J. L. |date=February 2014 |title=Fuel gain exceeding unity in an inertially confined fusion implosion |url=https://www.nature.com/articles/nature13008 |journal=Nature |language=en |volume=506 |issue=7488 |pages=343–348 |doi=10.1038/nature13008 |pmid=24522535 |bibcode=2014Natur.506..343H |s2cid=4466026 |issn=1476-4687 |access-date=July 25, 2023 |archive-date=November 18, 2023 |archive-url=https://web.archive.org/web/20231118212539/https://www.nature.com/articles/nature13008 |url-status=live }}</ref> This has been confused with having reached "]",<ref>{{cite web |last=Clery |first=Daniel |date=October 10, 2013 |title=Fusion "Breakthrough" at NIF? Uh, Not Really |url=http://news.sciencemag.org/physics/2013/10/fusion-breakthrough-nif-uh-not-really-%E2%80%A6 |website=ScienceInsider |access-date=November 3, 2013 |archive-date=October 16, 2013 |archive-url=https://web.archive.org/web/20131016065347/http://news.sciencemag.org/physics/2013/10/fusion-breakthrough-nif-uh-not-really-%E2%80%A6 |url-status=live }}</ref><ref>{{cite web |last=Hecht |first=Jeff |date=October 9, 2013 |title=Progress at NIF, but no 'breakthrough' |url=http://www.laserfocusworld.com/articles/2013/10/progress-at-nif-but-no-breakthrough.html |website=LaserFocusWorld |access-date=February 25, 2015 |archive-date=February 26, 2015 |archive-url=https://web.archive.org/web/20150226193850/http://www.laserfocusworld.com/articles/2013/10/progress-at-nif-but-no-breakthrough.html |url-status=live }}</ref> defined as the fusion energy exceeding the laser input energy.<ref name="scibr">{{cite web |last=Meade |first=Dale |date=October 11, 2013 |title=Scientific Breakeven for Fusion Energy |url=http://fire.pppl.gov/ICF_Scientific_Breakeven_LLNL2.pdf |access-date=February 26, 2015 |archive-date=February 26, 2015 |archive-url=https://web.archive.org/web/20150226190919/http://fire.pppl.gov/ICF_Scientific_Breakeven_LLNL2.pdf |url-status=live }}</ref> Using this definition gives 14.4 kJ out and 1.8 MJ in, a ratio of 0.008.<ref name=":2" /> | |||
=== Stockpile experiments, 2013–2015 === | |||
In 2013, NIF shifted focus to materials and weapons research. Experiments beginning in FY 2015 used plutonium targets.<ref>{{cite news |first=Jeremy |last=Thomas |url=http://www.contracostatimes.com/my-town/ci_27426991/despite-objections-lawrence-livermore-lab-go-forward-plutonium |title=Despite objections, Livermore lab to fire world's largest laser at plutonium |newspaper=Contra Cost Times |date=January 30, 2014 |access-date=April 16, 2015 |archive-date=April 2, 2015 |archive-url=https://web.archive.org/web/20150402185753/http://www.contracostatimes.com/my-town/ci_27426991/despite-objections-lawrence-livermore-lab-go-forward-plutonium |url-status=live }}</ref> Plutonium shots simulate the compression of the primary in a nuclear bomb by ]s, which had not seen direct testing since CNTB took effect. Plutonium use ranged from less than a milligram to 10 milligrams.<ref name="pumercury">{{cite news |last=Thomas |first=Jeremy |date=December 12, 2014 |title=Lawrence Livermore National Lab to test plutonium using NIF laser |newspaper=San Jose Mercury News |url=http://www.mercurynews.com/education/ci_27119177/lawrence-livermore-lab-test-plutonium-using-nif-laser |access-date=April 16, 2015 |archive-date=April 16, 2015 |archive-url=https://web.archive.org/web/20150416182710/http://www.mercurynews.com/education/ci_27119177/lawrence-livermore-lab-test-plutonium-using-nif-laser |url-status=live }}</ref> | |||
In FY 2014, NIF performed 191 shots, slightly more than one every two days. As of April 2015 NIF was on track to meet its goal of 300 laser shots in FY 2015.<ref>{{cite web |url=https://lasers.llnl.gov/news/efficiency-improvements |title=NIF Lasers Continue to Fire at a Record Rate |website=LLNL |access-date=April 16, 2015 |archive-date=April 18, 2015 |archive-url=https://web.archive.org/web/20150418124620/https://lasers.llnl.gov/news/efficiency-improvements |url-status=live }}</ref> | |||
=== Back to fusion, 2016–present === | |||
On January 28, 2016, NIF successfully executed its first gas pipe experiment intended to study the absorption of large amounts of laser light within {{convert|1|cm}} long targets relevant to high-gain ] (MagLIF). In order to investigate key aspects of the propagation, stability, and efficiency of laser energy coupling at full scale for high-gain MagLIF target designs, a single quad of NIF was used to deliver 30 kJ of energy to a target during a 13 nanosecond shaped pulse. Data return was favorable.<ref>{{Cite web |title=Experimental Highlights – 2016 |url=https://lasers.llnl.gov/news/experimental-highlights/2016/january |access-date=December 14, 2022 |website=lasers.llnl.gov |archive-date=December 14, 2022 |archive-url=https://web.archive.org/web/20221214194950/https://lasers.llnl.gov/news/experimental-highlights/2016/january |url-status=live }}</ref> | |||
In 2018, improvements in controlling compression asymmetry was demonstrated in a shot with an output of 1.9×10<sup>16</sup> neutrons, resulting in 0.054 MJ of fusion energy released by a 1.5 MJ laser pulse.<ref>{{cite journal |last1=Le Pape |first1=S. |last2=Berzak Hopkins |first2=L. F. |last3=Divol |first3=L. |last4=Pak |first4=A. |last5=Dewald |first5=E. L. |last6=Bhandarkar |first6=S. |last7=Bennedetti |first7=L. R. |last8=Bunn |first8=T. |last9=Biener |first9=J. |last10=Crippen |first10=J. |last11=Casey |first11=D. |last12=Edgell |first12=D. |last13=Fittinghoff |first13=D. N. |last14=Gatu-Johnson |first14=M.|author14-link=Maria Gatu Johnson |last15=Goyon |first15=C. |last16=Haan |first16=S. |last17=Hatarik |first17=R. |last18=Havre |first18=M. |last19=Ho |first19=D. D-M. |last20=Izumi |first20=N. |last21=Jaquez |first21=J. |last22=Khan |first22=S. F. |last23=Kyrala |first23=G. A. |last24=Ma |first24=T. |last25=Mackinnon |first25=A. J. |last26=MacPhee |first26=A. G. |last27=MacGowan |first27=B. J. |last28=Meezan |first28=N. B. |last29=Milovich |first29=J. |last30=Millot |first30=M. |last31=Michel |first31=P. |last32=Nagel |first32=S. R. |last33=Nikroo |first33=A. |last34=Patel |first34=P. |last35=Ralph |first35=J. |last36=Ross |first36=J. S. |last37=Rice |first37=N. G. |last38=Strozzi |first38=D. |last39=Stadermann |first39=M. |last40=Volegov |first40=P. |last41=Yeamans |first41=C. |last42=Weber |first42=C. |last43=Wild |first43=C. |last44=Callahan |first44=D. |last45=Hurricane |first45=O. A. |title=Fusion Energy Output Greater than the Kinetic Energy of an Imploding Shell at the National Ignition Facility |journal=Physical Review Letters |date=June 14, 2018 |volume=120 |issue=24 |page=245003 |doi=10.1103/PhysRevLett.120.245003 |pmid=29956968 |bibcode=2018PhRvL.120x5003L |hdl=1721.1/116411 |doi-access=free|hdl-access=free }}</ref> | |||
=== Burning plasma achieved, 2021 === | |||
] | |||
Experiments in 2020 and 2021 yielded the world's first ]s, in which most of the plasma heating came from nuclear fusion reactions.<ref name=":0">{{Cite journal |last1=Zylstra |first1=A. B. |last2=Hurricane |first2=O. A. |last3=Callahan |first3=D. A. |last4=Kritcher |first4=A. L. |last5=Ralph |first5=J. E. |last6=Robey |first6=H. F. |last7=Ross |first7=J. S. |last8=Young |first8=C. V. |last9=Baker |first9=K. L.|last10=Casey|first10=D. T. |last11=Döppner |first11=T. |date=2022 |title=Burning plasma achieved in inertial fusion |journal=Nature |volume=601 |issue=7894 |pages=542–548 |doi=10.1038/s41586-021-04281-w |pmid=35082418 |pmc=8791836 |bibcode=2022Natur.601..542Z |issn=1476-4687}}</ref> This result was followed on August 8, 2021 by the world's first ] plasma, in which the fusion heating was sufficient to sustain the thermonuclear reaction.<ref name="ignition">{{Cite journal |last1=Indirect Drive ICF Collaboration |last2=Abu-Shawareb |first2=H. |last3=Acree |first3=R. |last4=Adams |first4=P. |last5=Adams |first5=J. |last6=Addis |first6=B. |last7=Aden |first7=R. |last8=Adrian |first8=P. |last9=Afeyan |first9=B. B. |last10=Aggleton |first10=M. |last11=Aghaian |first11=L. |last12=Aguirre |first12=A. |last13=Aikens |first13=D. |last14=Akre |first14=J. |last15=Albert |first15=F. |date=August 8, 2022 |title=Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment |url=https://link.aps.org/doi/10.1103/PhysRevLett.129.075001 |journal=Physical Review Letters |volume=129 |issue=7 |page=075001 |doi=10.1103/PhysRevLett.129.075001 |pmid=36018710 |bibcode=2022PhRvL.129g5001A |hdl=10044/1/99300 |s2cid=250321131 |hdl-access=free |access-date=August 14, 2022 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082140/https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.075001 |url-status=live }}</ref><ref>{{Cite journal |last1=Zylstra |first1=A. B. |last2=Kritcher |first2=A. L. |last3=Hurricane |first3=O. A. |last4=Callahan |first4=D. A. |last5=Ralph |first5=J. E. |last6=Casey |first6=D. T. |last7=Pak |first7=A. |last8=Landen |first8=O. L. |last9=Bachmann |first9=B. |last10=Baker |first10=K. L. |last11=Berzak Hopkins |first11=L. |last12=Bhandarkar |first12=S. D. |last13=Biener |first13=J. |last14=Bionta |first14=R. M. |last15=Birge |first15=N. W. |date=August 8, 2022 |title=Experimental achievement and signatures of ignition at the National Ignition Facility |url=https://link.aps.org/doi/10.1103/PhysRevE.106.025202 |journal=Physical Review E |volume=106 |issue=2 |page=025202 |doi=10.1103/PhysRevE.106.025202 |pmid=36109932 |bibcode=2022PhRvE.106b5202Z |osti=1959535 |s2cid=251451927 |access-date=August 14, 2022 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082144/https://journals.aps.org/pre/abstract/10.1103/PhysRevE.106.025202 |url-status=live }}</ref><ref>{{Cite web |last=Laboratory |first=Lawrence Livermore National |date=August 14, 2022 |title=Nuclear Fusion Energy Breakthrough: Ignition Confirmed in Record 1.3 Megajoule Shot |url=https://scitechdaily.com/nuclear-fusion-energy-breakthrough-ignition-confirmed-in-record-1-3-megajoule-shot/ |access-date=August 14, 2022 |website=SciTechDaily |archive-date=August 14, 2022 |archive-url=https://web.archive.org/web/20220814093803/https://scitechdaily.com/nuclear-fusion-energy-breakthrough-ignition-confirmed-in-record-1-3-megajoule-shot/ |url-status=live }}</ref> It produced excess neutrons consistent with a short-lived chain reaction of around 100 trillionths of a second.<ref>{{Cite news |last=Ball |first=Philip |title=U.S. Project Reaches Major Milestone toward Practical Fusion Power |url=https://www.scientificamerican.com/article/u-s-project-reaches-major-milestone-toward-practical-fusion-power/ |access-date=February 11, 2022 |website=Scientific American |language=en |archive-date=February 11, 2022 |archive-url=https://web.archive.org/web/20220211125844/https://www.scientificamerican.com/article/u-s-project-reaches-major-milestone-toward-practical-fusion-power/ |url-status=live }}</ref><ref>{{Cite journal |last1=Kritcher |first1=A. L. |author-link=Andrea Lynn Kritcher |last2=Zylstra |first2=A. B. |last3=Callahan |first3=D. A. |last4=Hurricane |first4=O. A. |last5=Weber |first5=C. R. |last6=Clark |first6=D. S. |last7=Young |first7=C. V. |last8=Ralph |first8=J. E. |last9=Casey |first9=D. T. |last10=Pak |first10=A. |last11=Landen |first11=O. L. |last12=Bachmann |first12=B. |last13=Baker |first13=K. L. |last14=Berzak Hopkins |first14=L. |last15=Bhandarkar |first15=S. D. |date=August 8, 2022 |title=Design of an inertial fusion experiment exceeding the Lawson criterion for ignition |journal=Physical Review E |volume=106 |issue=2 |page=025201 |doi=10.1103/PhysRevE.106.025201 |pmid=36110025 |bibcode=2022PhRvE.106b5201K |s2cid=251457864|doi-access=free }}</ref> | |||
The fusion energy yield of the 2021 experiment was estimated to be 70% of the laser energy incident on the plasma. This result slightly beat the former record of 67% set by the ] torus in 1997.<ref>{{Cite news |url=https://www.nytimes.com/2021/08/17/science/lasers-fusion-power-watts-earth.html |title=Laser Fusion Experiment Unleashes an Energetic Burst of Optimism |first=Kenneth |last=Chang |date=August 17, 2021 |archive-url=https://web.archive.org/web/20210817201327/https://www.nytimes.com/2021/08/17/science/lasers-fusion-power-watts-earth.html |archive-date=August 17, 2021 |newspaper=The New York Times |access-date=August 18, 2021}}</ref>{{Failed verification|date=December 2022}} Taking the energy efficiency of the laser itself into account, the experiment used about 477 MJ of electrical energy to get 1.8 MJ of energy into the target to create 1.3 MJ of fusion energy.<ref name=":0" /> | |||
Several design changes enabled this result. The material of the capsule shell was changed to diamond to increase the absorbance of secondary x-rays created by the laser burst, thus increasing the efficacy of the collapse, and its surface was further smoothed. The size of the hole in the capsule used to inject fuel was reduced. The holes in the gold cylinder surrounding the capsule were shrunk to reduce energy loss. The laser pulse was extended.<ref>{{Cite web |last=Clery |first=Daniel |date=August 17, 2021 |title=With explosive new result, laser-powered fusion effort nears 'ignition' |url=https://www.science.org/content/article/explosive-new-result-laser-powered-fusion-effort-nears-ignition |access-date=August 18, 2021 |website=Science |publisher=AAAS |language=en |archive-date=February 3, 2023 |archive-url=https://web.archive.org/web/20230203063649/https://www.science.org/content/article/explosive-new-result-laser-powered-fusion-effort-nears-ignition |url-status=live }}</ref> | |||
=== Scientific breakeven achieved, 2022 {{anchor|Achieving ignition}} === | |||
{{Self-contradictory|section|about=the amount of energy produced by the first scientific breakeven|date=May 2024}} | |||
] | |||
] speaks at the December 13, 2022 ] announcing breakeven ignition.]] | |||
{{anchor|December 2022}} | |||
The NIF became the first fusion experiment to achieve ] on December 5, 2022, with an experiment producing 3.15 megajoules of energy from a 2.05 megajoule input of laser light for an energy gain of about 1.5.<ref name="igntion2022-llnl">{{Cite web |title=National Ignition Facility achieves fusion ignition |url=https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition |access-date=December 13, 2022 |website=www.llnl.gov |language=en |archive-date=December 13, 2022 |archive-url=https://web.archive.org/web/20221213212403/https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition |url-status=live }}</ref><ref>{{Cite web |title=DOE National Laboratory Makes History by Achieving Fusion Ignition |url=https://www.energy.gov/articles/doe-national-laboratory-makes-history-achieving-fusion-ignition |access-date=December 13, 2022 |website=Energy.gov |language=en |archive-date=February 19, 2023 |archive-url=https://web.archive.org/web/20230219060607/https://www.energy.gov/articles/doe-national-laboratory-makes-history-achieving-fusion-ignition |url-status=live }}</ref><ref>{{cite news |newspaper=The New York Times |title=Scientists Achieve Nuclear Fusion Breakthrough With Blast of 192 Lasers |author=Kenneth Chang |date=December 13, 2022 |url=https://www.nytimes.com/2022/12/13/science/nuclear-fusion-energy-breakthrough.html |access-date=December 13, 2022 |archive-date=December 14, 2022 |archive-url=https://web.archive.org/web/20221214172447/https://www.nytimes.com/2022/12/13/science/nuclear-fusion-energy-breakthrough.html |url-status=live }}</ref><ref>{{cite web |last1=Bush |first1=Evan |last2=Lederman |first2=Josh |date=December 13, 2022 |title=We have 'ignition': Fusion breakthrough draws energy gain |url=https://www.nbcnews.com/science/science-news/fusion-breakthrough-net-energy-gain-rcna61326 |access-date=December 13, 2022 |website=] |archive-date=December 13, 2022 |archive-url=https://web.archive.org/web/20221213154912/https://www.nbcnews.com/science/science-news/fusion-breakthrough-net-energy-gain-rcna61326 |url-status=live }}</ref><ref>{{Cite web |date=February 6, 2024 |title=NIF fusion breakeven claims peer reviewed and verified by multiple teams |url=https://phys.org/news/2024-02-nif-fusion-breakeven-peer-multiple.html |website=phys.org |access-date=June 8, 2024 |archive-date=February 24, 2024 |archive-url=https://web.archive.org/web/20240224165434/https://phys.org/news/2024-02-nif-fusion-breakeven-peer-multiple.html |url-status=live }}</ref> Charging the laser consumed "well above 400 megajoules".<ref>{{Cite web|url=https://www.cnet.com/science/major-energy-breakthrough-milestone-achieved-in-us-fusion-experiment/|title=Major Energy Breakthrough: Milestone Achieved in US Fusion Experiment|first=Jackson|last=Ryan|website=CNET|access-date=December 16, 2022|archive-date=December 21, 2022|archive-url=https://web.archive.org/web/20221221212615/https://www.cnet.com/science/major-energy-breakthrough-milestone-achieved-in-us-fusion-experiment/|url-status=live}}</ref> In a public announcement on December 13, the Secretary of Energy ] announced the facility had achieved ignition.<ref>{{cite news |last=Woodward |first=Aylin |date=December 13, 2022 |title=Nuclear-Fusion Energy Breakthrough Reported by Scientists at U.S. Lab |publisher=] |url=https://www.wsj.com/articles/nuclear-fusion-energy-breakthrough-reported-by-scientists-at-u-s-lab-11670944595?mod=hp_lead_pos10 |access-date=December 13, 2022 |archive-date=December 13, 2022 |archive-url=https://web.archive.org/web/20221213152941/https://www.wsj.com/articles/nuclear-fusion-energy-breakthrough-reported-by-scientists-at-u-s-lab-11670944595?mod=hp_lead_pos10 |url-status=live }}</ref> While this was often characterized as a "net energy gain" from fusion, this was only true with respect to the energy delivered by the laser; reports sometimes omitted the ~300 MJ power input required.<ref name=":6" /><ref name=":5" /><ref name=":4" /> | |||
The feat required the use of a slightly thicker and smoother capsule surrounding the fuel and a 2.05 MJ laser (up from 1.9 MJ in 2021), yielding 3.15 MJ, a 54% surplus.<ref>{{Cite journal |url=https://www.science.org/content/article/news-glance-more-success-fusion-medical-tests-under-scrutiny-and-grizzly-reintroduction |title=Fusion update |journal=Science |access-date=October 9, 2023 |archive-date=October 10, 2023 |archive-url=https://web.archive.org/web/20231010025300/https://www.science.org/content/article/news-glance-more-success-fusion-medical-tests-under-scrutiny-and-grizzly-reintroduction |url-status=live }}</ref> They also redistributed the energy among the split laser beams, which produced a more symmetrical (spherical) implosion.<ref name=":1" /> | |||
The NIF achieved breakeven for a second time on July 30, 2023 yielding 3.88 MJ, an 89% surplus.<ref name="repeatOn30jul2023">{{Cite web |last=Lavanya Ahire in Bengaluru and Doina Chiacu in Washington; additional reporting by Yana Gaur |date=August 7, 2023 |editor-last=Adler |editor-first=Leslie |editor2-last=Craft |editor2-first=Diane |title=US scientists repeat fusion ignition breakthrough for 2nd time |url=https://www.reuters.com/business/energy/us-scientists-repeat-fusion-power-breakthrough-ft-2023-08-06/ |website=Reuters |access-date=June 8, 2024 |archive-date=December 13, 2023 |archive-url=https://web.archive.org/web/20231213220633/http://www.reuters.com/business/energy/us-scientists-repeat-fusion-power-breakthrough-ft-2023-08-06/ |url-status=live }}</ref><ref name=":3" /> At least four of six shots performed after the first successful one in December 2022 achieved breakeven.<ref>{{Cite web |title=Momentary Fusion Breakthroughs Face Hard Reality > New NIF data yields promise, though road to repeatability remains long |url=https://spectrum.ieee.org/video-friday-1x-robots-tidy-up |website=IEEE Spectrum |access-date=June 8, 2024 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082647/https://spectrum.ieee.org/video-friday-1x-robots-tidy-up |url-status=live }}</ref> These successes led the DOE to fund three additional research centers.<ref name=":3">{{Cite journal |last=Tollefson |first=Jeff |date=2023-12-15 |title=US nuclear-fusion lab enters new era: achieving 'ignition' over and over |url=https://www.nature.com/articles/d41586-023-04045-8 |journal=Nature |volume=625 |issue=7993 |pages=11–12 |language=en |doi=10.1038/d41586-023-04045-8 |pmid=38102381 |s2cid=266311829 |access-date=December 19, 2023 |archive-date=June 8, 2024 |archive-url=https://web.archive.org/web/20240608082654/https://www.nature.com/articles/d41586-023-04045-8 |url-status=live }}</ref> Lawrence Livermore planned to raise laser energy to 2.2 MJ per shot through upgraded optics and lasers {{circa|2023}},<ref>{{cite news|newspaper=The New York Times|title=A Laser Fusion Breakthrough Gets a Bigger Burst of Energy|author=Kenneth Chang|date=September 25, 2023|url=https://www.nytimes.com/2023/09/25/science/nuclear-laser-fusion-nif.html|access-date=September 26, 2023|archive-date=June 8, 2024|archive-url=https://web.archive.org/web/20240608082648/https://www.nytimes.com/2023/09/25/science/nuclear-laser-fusion-nif.html|url-status=live}}</ref><ref>{{cite web|title=FY 2022 Annual Report National Ignition Facility - 2022|publisher=Lawrence Livermore National Laboratory|access-date=September 26, 2023|url=https://annual.llnl.gov/fy-2022/national-ignition-facility-2022|archive-date=September 26, 2023|archive-url=https://web.archive.org/web/20230926211321/https://annual.llnl.gov/fy-2022/national-ignition-facility-2022|url-status=live}}</ref> reaching it on the experiment held on October 30, 2023.<ref name=":3" /> | |||
== Similar projects == | |||
Some similar experimental ICF projects are: | |||
{{colbegin}} | |||
* ] (LMJ)<ref>{{cite web |title=HiPER |url=http://www-lmj.cea.fr/ |publisher=LMF Project |date=2009 |access-date=June 2, 2010 |archive-date=October 2, 2018 |archive-url=https://web.archive.org/web/20181002073018/http://www-lmj.cea.fr/ |url-status=live }}</ref> | |||
* ] | |||
* ] (HiPER)<ref>{{cite web |title=HiPER |url=http://www.hiper-laser.org/ |publisher=HiPER Project |date=2009 |access-date=May 29, 2009 |archive-date=March 3, 2011 |archive-url=https://web.archive.org/web/20110303190444/http://www.hiper-laser.org/ |url-status=dead }}</ref> | |||
* ] (LLE) | |||
* ] (MagLIF)<ref>{{cite web |title=Dry-Run Experiments Verify Key Aspect of Nuclear Fusion Concept: Scientific 'Break-Even' or Better Is Near-Term Goal |url=https://www.sciencedaily.com/releases/2012/09/120917124210.htm |access-date=September 24, 2012 |archive-date=September 23, 2012 |archive-url=https://web.archive.org/web/20120923144905/http://www.sciencedaily.com/releases/2012/09/120917124210.htm |url-status=live }}</ref> | |||
* ]<ref>{{cite web |title=Shenguang-II High Power Laser |url=http://caod.oriprobe.com/articles/10880138/Shenguang__%E2%85%A1__High_Power_Laser_Facility.htm |publisher=] |access-date=June 12, 2014 |archive-date=September 8, 2015 |archive-url=https://web.archive.org/web/20150908212244/http://caod.oriprobe.com/articles/10880138/Shenguang__%E2%85%A1__High_Power_Laser_Facility.htm |url-status=live }}</ref> | |||
{{colend}} | |||
== Pictures == | |||
<gallery mode="packed" heights="150px"> | |||
File:Viewing port.jpg|Viewing port allows a look into the interior of the 30 foot diameter target chamber. | |||
File:NIF target chamber exterior.jpg|Exterior view of the upper third of the target chamber. The large square beam ports are prominent. | |||
File:National Ignition Facility diagnostic handling instrument.jpg|A technician loads an instrument canister into the vacuum-sealed diagnostic instrument manipulator. | |||
File:nif flashlamps.jpg|The flashlamps used to pump the main amplifiers are the largest ever in commercial production. | |||
File:Laser glass slabs.jpg|The glass slabs used in the amplifiers are likewise much larger than those used in previous lasers. | |||
</gallery> | </gallery> | ||
== In popular culture == | |||
==References== | |||
The NIF was used as the set for the ]'s ] in the 2013 movie '']''.<ref>{{cite web |last1=Bishop |first1=Breanna |title=National Ignition Facility provides backdrop for "Star Trek: Into Darkness" |url=https://www.llnl.gov/news/national-ignition-facility-provides-backdrop-star-trek-darkness |website=Lawrence Livermore National Laboratory |access-date=November 19, 2015 |archive-date=November 20, 2015 |archive-url=https://web.archive.org/web/20151120000536/https://www.llnl.gov/news/national-ignition-facility-provides-backdrop-star-trek-darkness |url-status=live }}</ref> | |||
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== See also == | ||
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== Notes == | |||
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== References == | |||
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== External links == | |||
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{{Commons category|National Ignition Facility}} | |||
*{{Cite web |date=May 27, 2010 |title=National Ignition Facility: How NIF Works, NIF & Photon Science |url=https://lasers.llnl.gov/about/nif/how_nif_works/index.php |access-date=December 5, 2020 |archive-url=https://web.archive.org/web/20100527152319/https://lasers.llnl.gov/about/nif/how_nif_works/index.php |archive-date=May 27, 2010}} | |||
*{{Cite web |title=Lasers, Photonics, and Fusion Science: Science and Technology on a Mission |url=https://lasers.llnl.gov/ |access-date=December 5, 2020 |website=lasers.llnl.gov}} | |||
*{{Cite magazine |archive-date=October 2, 2011 |title=NIF Director, Dr Ed Moses, on the progress of the facility |url=http://www.ingenia.org.uk/ingenia/articles.aspx?Index=466 |archive-url=https://web.archive.org/web/20111002145910/http://www.ingenia.org.uk/ingenia/articles.aspx?Index=466 |access-date=December 5, 2020 |magazine=Ingenia |date=December 2007}} | |||
*{{Cite web |title=NIF project director Moses says facility is ready to go |url=https://spie.org/news/0324-nif-to-launch |access-date=December 5, 2020 |website=spie.org}} | |||
*{{Cite web |date=November 13, 2009 |title=Inside Livermore Lab's Race to Invent Clean Energy |url=https://www.newsweek.com/inside-livermore-labs-race-invent-clean-energy-77037 |access-date=December 5, 2020 |website=Newsweek |language=en}} | |||
*{{Cite web |last=Eric |title=NIF Laser Fusion in Fulldome |date=April 10, 2011 |url=http://www.xrez.com/case-studies/nif-laser-fusion-in-fulldome/ |access-date=December 5, 2020 |language=en-US}} | |||
*{{Cite journal |last1=Clery |first1=Daniel |date=November 23, 2020 |title=Laser fusion reactor approaches 'burning plasma' milestone |url=https://www.science.org/content/article/laser-fusion-reactor-approaches-burning-plasma-milestone |access-date=December 5, 2020 |journal=Science |volume=370 |issue=6520 |pages=1019–1020 |doi=10.1126/science.370.6520.1019 |pmid=33243866 |bibcode=2020Sci...370.1019C |s2cid=227182275 |language=en}} | |||
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Latest revision as of 00:04, 15 December 2024
American nuclear fusion facility
The National Ignition Facility (NIF) is a laser-based inertial confinement fusion (ICF) research device, located at Lawrence Livermore National Laboratory in Livermore, California, United States. NIF's mission is to achieve fusion ignition with high energy gain. It achieved the first instance of scientific breakeven controlled fusion in an experiment on December 5, 2022, with an energy gain factor of 1.5. It supports nuclear weapon maintenance and design by studying the behavior of matter under the conditions found within nuclear explosions.
NIF is the largest and most powerful ICF device built to date. The basic ICF concept is to squeeze a small amount of fuel to reach pressure and temperature necessary for fusion. NIF hosts the world's most energetic laser. The laser indirectly heats the outer layer of a small sphere. The energy is so intense that it causes the sphere to implode, squeezing the fuel inside. The implosion reaches a peak speed of 350 km/s (0.35 mm/ns), raising the fuel density from about that of water to about 100 times that of lead. The delivery of energy and the adiabatic process during implosion raises the temperature of the fuel to hundreds of millions of degrees. At these temperatures, fusion processes occur in the tiny interval before the fuel explodes outward.
Construction on the NIF began in 1997. NIF was completed five years behind schedule and cost almost four times its original budget. Construction was certified complete on March 31, 2009, by the U.S. Department of Energy. The first large-scale experiments were performed in June 2009 and the first "integrated ignition experiments" (which tested the laser's power) were declared completed in October 2010.
From 2009 to 2012 experiments were conducted under the National Ignition Campaign, with the goal of reaching ignition just after the laser reached full power, some time in the second half of 2012. The campaign officially ended in September 2012, at about 1⁄10 the conditions needed for ignition. Thereafter NIF has been used primarily for materials science and weapons research. In 2021, after improvements in fuel target design, NIF produced 70% of the energy of the laser, beating the record set in 1997 by the JET reactor at 67% and achieving a burning plasma. On December 5, 2022, after further technical improvements, NIF reached "ignition", or scientific breakeven, for the first time, achieving a 154% energy yield compared to the input energy. However, while this was scientifically a success, the experiment in practice produced less than 1% of the energy the facility used to create it: while 3.15 MJ of energy was yielded from 2.05 MJ input, the lasers delivering the 2.05 MJ of energy took about 300 MJ to produce in the facility.
Inertial confinement fusion basics
Main article: ICF mechanismInertial confinement fusion (ICF) devices use intense energy to rapidly heat the outer layers of a target in order to compress it. Nuclear fission provides the energy source for thermonuclear warheads, while sources such as laser beams and particle beams are used in non-weapon devices.
The target is a small spherical pellet containing a few milligrams of fusion fuel, typically a mix of deuterium (D) and tritium (T), as this composition has the lowest ignition temperature.
The lasers can either heat the surface of the fuel pellet directly – known as direct drive – or heat the inner surface of a hollow metal cylinder around the pellet – known as indirect drive. In the indirect drive case, the cylinder, called a hohlraum (German for 'hollow room' or 'cavity'), becomes hot enough to re-emit the energy as even higher frequency X-rays. These X-rays, which are more symmetrically distributed than the original laser light, heat the surface of pellet.
In either case, the material on the outside of the pellet is turned into a plasma, which explodes away from the surface. The rest of the pellet is driven inward on all sides, into a small volume of extremely high density. The surface explosion creates shock waves that travel inward. At the center of the fuel, a small volume is further heated and compressed. When the temperature and density are high enough, fusion reactions occur. The energy must be delivered quickly and spread extremely evenly across the target's outer surface in order to compress the fuel symmetrically.
The reactions release high-energy particles, some of which, primarily alpha particles, collide with unfused fuel and heat it further, potentially triggering additional fusion. At the same time, the fuel is also losing heat through x-ray losses and hot electrons leaving the fuel area. Thus the rate of alpha heating must be greater than the loss rate, termed bootstrapping. Given the right conditions—high enough density, temperature, and duration—bootstrapping results in a chain reaction, burning outward from the center. This is known as ignition, which fuses a significant portion of the fuel and releases large amounts of energy.
As of 1998, most ICF experiments had used laser drivers. Other drivers have been examined, such as heavy ions driven by particle accelerators.
Design
System
NIF primarily uses the indirect drive method of operation, in which the laser heats a small metal cylinder surrounding the capsule inside it, which then emits X-rays that heat the fuel pellet. Experimental systems, including the OMEGA and Nova lasers, validated this approach. The NIF's high power supports a much larger target than OMEGA or Nova; the baseline pellet design is about 2 mm in diameter. It is chilled to about 18 kelvin (−255 °C) and lined with a layer of frozen deuterium–tritium (DT) fuel. The hollow interior contains a small amount of DT gas.
In a typical experiment, the laser generates 3 MJ of infrared laser energy of a possible 4. About 1.5 MJ remains after conversion to UV, and another 15 percent is lost in the hohlraum. About 15 percent of the resulting x-rays, about 150 kJ, are absorbed by the target's outer layers. The coupling between the capsule and the x-rays is lossy, and ultimately only about 10 to 14 kJ of energy is deposited in the fuel.
The fuels in the center of the target are compressed to a density of about 1000 g/cm For comparison, lead has a density of about 11 g/cm. The pressure is the equivalent of 300 billion atmospheres.
Before NIF was constructed, it was expected based on simulations that 10–15 MJ of fusion energy would be released, resulting in a net fusion energy gain, denoted Q, of about 5–8 (fusion energy out/UV laser energy in). Due to the design of the target chamber, the baseline design limited the maximum possible fusion energy release to 45 MJ, equivalent to about 11 kg of TNT exploding. When NIF was built and used in 2011, the fusion energy was far lower than expected – less than 1 kJ. Performance was gradually improved until, as of 2024, the fusion energy routinely exceeded 2 MJ.
To be useful for energy production, a fusion facility must produce fusion output at least an order of magnitude more than the energy used to power the laser amplifiers – 400 MJ in the case of NIF. Commercial laser fusion systems would use much more efficient diode-pumped solid state lasers, where wall-plug efficiencies of 10 percent have been demonstrated, and efficiencies 16–18 percent were expected with advanced concepts under development in 1996.
Laser
As of 2010 NIF aimed to create a single 500 terawatt (TW) peak flash of light that reaches the target from numerous directions within a few picoseconds. The design uses 192 beamlines in a parallel system of flashlamp-pumped, neodymium-doped phosphate glass lasers.
To ensure that the output of the beamlines is uniform, the laser is amplified from a single source in the Injection Laser System (ILS). This starts with a low-power flash of 1053-nanometer (nm) infrared light generated in an ytterbium-doped optical fiber laser termed Master Oscillator. Its light is split and directed into 48 Preamplifier Modules (PAMs). Each PAM conducts a two-stage amplification process via xenon flash lamps. The first stage is a regenerative amplifier in which the pulse circulates 30 to 60 times, increasing its energy from nanojoules to tens of millijoules. The second stage sends the light four times through a circuit containing a neodymium glass amplifier similar to (but much smaller than) the ones used in the main beamlines, boosting the millijoules to about 6 joules. According to LLNL, designing the PAMs was one of the major challenges. Subsequent improvements allowed them to surpass their initial design goals.
The main amplification takes place in a series of glass amplifiers located at one end of the beamlines. Before firing, the amplifiers are first optically pumped by a total of 7,680 flash lamps. The lamps are powered by a capacitor bank that stores 400 MJ (110 kWh). When the wavefront passes through them, the amplifiers release some of the energy stored in them into the beam. The beams are sent through the main amplifier four times, using an optical switch located in a mirrored cavity. These amplifiers boost the original 6 J to a nominal 4 MJ. Given the time scale of a few nanoseconds, the peak UV power delivered to the target reaches 500 TW.
Near the center of each beamline, and taking up the majority of the total length, are spatial filters. These consist of long tubes with small telescopes at the end that focus the beam to a tiny point in the center of the tube, where a mask cuts off any stray light outside the focal point. The filters ensure that the beam image is extremely uniform. Spatial filters were a major step forward. They were introduced in the Cyclops laser, an earlier LLNL experiment.
The end-to-end length of the path the laser beam travels, including switches, is about 1,500 metres (4,900 ft). The various optical elements in the beamlines are generally packaged into Line Replaceable Units (LRUs), standardized boxes about the size of a vending machine that can be dropped out of the beamline for replacement from below.
After amplification is complete the light is switched back into the beamline, where it runs to the far end of the building to the target chamber. The target chamber is a 10-metre-diameter (33 ft) multi-piece steel sphere weighing 130,000 kilograms (290,000 lb). Just before reaching the target chamber, the light is reflected off mirrors in the switchyard and target area in order to hit the target from different directions. Since the path length from the Master Oscillator to the target is different for each beamline, optics are used to delay the light in order to ensure that they all reach the center within a few picoseconds of each other.
One of the last steps before reaching the target chamber is to convert the infrared (IR) light at 1053 nm into the ultraviolet (UV) at 351 nm in a device known as a frequency converter. These are made of thin sheets (about 1 cm thick) cut from a single crystal of potassium dihydrogen phosphate. When the 1053 nm (IR) light passes through the first of two of these sheets, frequency addition converts a large fraction of the light into 527 nm light (green). On passing through the second sheet, frequency combination converts much of the 527 nm light and the remaining 1053 nm light into 351 nm (UV) light. Infrared (IR) light is much less effective than UV at heating the targets, because IR couples more strongly with hot electrons that absorb a considerable amount of energy and interfere with compression. The conversion process can reach peak efficiencies of about 80 percent for a laser pulse that has a flat temporal shape, but the temporal shape needed for ignition varies significantly over the duration of the pulse. The actual conversion process is about 50 percent efficient, reducing delivered energy to a nominal 1.8 MJ.
As of 2010, one important aspect of any ICF research project was ensuring that experiments could be carried out on a timely basis. Previous devices generally had to cool down for many hours to allow the flashlamps and laser glass to regain their shapes after firing (due to thermal expansion), limiting their use to one or fewer firings per day. One of the goals for NIF has been to reduce this time to less than four hours, in order to allow 700 firings a year.
Other concepts
NIF is also exploring new types of targets. Previous experiments generally used plastic ablators, typically polystyrene (CH). NIF targets are constructed by coating a plastic form with a layer of sputtered beryllium or beryllium–copper alloy, and then oxidizing the plastic out of the center. Beryllium targets offer higher implosion efficiencies from x-ray inputs.
Although NIF was primarily designed as an indirect drive device, the energy in the laser as of 2008 was high enough to be used as a direct drive system, where the laser shines directly on the target without conversion to x-rays. The power delivered by NIF UV rays was estimated to be more than enough to cause ignition, allowing fusion energy gains of about 40x, somewhat higher than the indirect drive system.
As of 2005, scaled implosions on the OMEGA laser and computer simulations showed NIF to be capable of ignition using a polar direct drive (PDD) configuration where the target was irradiated directly by the laser only from the top and bottom, without changes to the NIF beamline layout.
As of 2005, other targets, called saturn targets, were specifically designed to reduce the anisotropy and improve the implosion. They feature a small plastic ring around the "equator" of the target, which becomes a plasma when hit by the laser. Some of the laser light is refracted through this plasma back towards the equator of the target, evening out the heating. NIF ignition with gains of just over 35 times are thought to be possible, producing results almost as good as the fully symmetric direct drive approach.
History
Impetus, 1957
The history of ICF at Lawrence Livermore National Laboratory in Livermore, California, started with physicist John Nuckolls, who started considering the problem after a 1957 meeting arranged by Edward Teller there. During these meetings, the idea later known as PACER emerged. PACER envisioned the explosion of small hydrogen bombs in large caverns to generate steam that would be converted into electrical power. After identifying problems with this approach, Nuckolls wondered how small a bomb could be made that would still generate net positive power.
A typical hydrogen bomb has two parts: a plutonium-based fission bomb known as the primary, and a cylindrical arrangement of fusion fuels known as the secondary. The primary releases x-rays, which are trapped within the bomb casing. They heat and compress the secondary until it ignites. The secondary consists of lithium deuteride (LiD) fuel, which requires an external neutron source. This is normally in the form of a small plutonium "spark plug" in the center of the fuel. Nuckolls's idea was to explore how small the secondary could be made, and what effects this would have on the energy needed from the primary to cause ignition. The simplest change is to replace the LiD fuel with DT gas, removing the need for the spark plug. This allows secondaries of any size – as the secondary shrinks, so does the amount of energy needed for ignition. At the milligram level, the energy levels started to approach those available through several known devices.
By the early 1960s, Nuckolls and several other weapons designers had developed ICF's outlines. The DT fuel would be placed in a small capsule, designed to rapidly ablate when heated and thereby maximize compression and shock wave formation. This capsule would be placed within an engineered shell, the hohlraum, which acts like the bomb casing. The hohlraum did not have to be heated by x-rays; any source of energy could be used as long as it delivered enough energy to heat the hohlraum and produce x-rays. Ideally the energy source would be located some distance away, to mechanically isolate both ends of the reaction. A small atomic bomb could be used as the energy source, as in a hydrogen bomb, but ideally smaller energy sources would be used. Using computer simulations, the teams estimated that about 5 MJ of energy would be needed from the primary, generating a 1 MJ beam. To put this in perspective, a small (0.5 kt ) fission primary releases 2 TJ.
ICF program, 1970s
While Nuckolls and LLNL were working on hohlraum-based concepts, UCSD physicist Keith Brueckner was independently working on direct drive. In the early 1970s, Brueckner formed KMS Fusion to commercialize this concept. This sparked an intense rivalry between KMS and the weapons labs. Formerly ignored, ICF became a hot topic and most of the labs started ICF work. LLNL decided to concentrate on glass lasers, while other facilities studied gas lasers using carbon dioxide (e.g. ANTARES, Los Alamos National Laboratory) or KrF (e.g. Nike laser, Naval Research Laboratory).
Throughout these early stages, much of the understanding of the fusion process was the result of computer simulations, primarily LASNEX. LASNEX simplified the reaction to a 2-dimensional approximation, which was all that was possible with the available computing power. LASNEX estimated that laser drivers in the kJ range could reach low gain, which was just within the state of the art. This led to the Shiva laser project which was completed in 1977. Shiva fell far short of its goals. The densities reached were thousands of times smaller than predicted. This was traced to issues with the way the laser delivered heat to the target. Most of its energy energized electrons rather than the entire fuel mass. Further experiments and simulations demonstrated that this process could be dramatically improved by using shorter wavelengths.
Further upgrades to the simulation programs, accounting for these effects, predicted that a different design would reach ignition. This system took the form of the 20-beam 200 kJ Nova laser. During the construction phase, Nuckolls found an error in his calculations, and an October 1979 review chaired by former LLNL director John S. Foster Jr. confirmed that Nova would not reach ignition. It was modified into a smaller 10-beam design that converted the light to 351 nm and increase coupling efficiency. Nova was able to deliver about 30 kJ of UV laser energy, about half of what was expected, primarily due to optical damage to the final focusing optics. Even at those levels, it was clear that the predictions for fusion production were wrong; even at the limited powers available, fusion yields were far below predictions.
Halite and Centurion, 1978
Each experiment showed that the energy needed to reach ignition continued to be underestimated. The Department of Energy (DOE) decided that direct experimentation was the best way to settle the issue, and in 1978 they started a series of underground experiments at the Nevada Test Site that used small nuclear bombs to illuminate ICF targets. The tests were known as Halite (LLNL) and Centurion (LANL).
The basic concept behind the tests had been developed in the 1960s as a way to develop anti-ballistic missile warheads. It was found that bombs that exploded outside the atmosphere gave off bursts of X-rays that could damage an enemy warhead at long range. To test the effectiveness of this system, and to develop countermeasures to protect US warheads, the Defense Atomic Support Agency (now the Defense Threat Reduction Agency) developed a system that placed the targets at the end of long tunnels behind fast-shutting doors. The doors were timed to shut in the brief period between the arrival of the X-rays and the subsequent blast. This saved the reentry vehicle (RV) from blast damage and allowed them to be inspected.
ICF tests used the same system, replacing the RVs by hohlraums. Each test simultaneously illuminated many targets, each at a different distance from the bomb to test the effect of varying of illumination. Another question was how large the fuel assembly had to be in order for the fuel to self-heat from the fusion reactions and thus reach ignition. Initial data were available by mid-1984, and the testing ceased in 1988. Ignition was achieved for the first time during these tests. The amount of energy and the size of the fuel targets needed to reach ignition was far higher than predicted. During this same period, experiments began on Nova using similar targets to understand their behavior under laser illumination, allowing direct comparison against the bomb tests.
This data suggested that about 10 MJ of X-ray energy would be needed to reach ignition, far beyond what had earlier been calculated. If those X-rays are created by beaming an IR laser to a hohlraum, as in Nova or NIF, then dramatically more laser energy would be required, on the order of 100 MJ.
This triggered a debate in the ICF community. One group suggested an attempt to build a laser of this power; Leonardo Mascheroni and Claude Phipps designed a new type of hydrogen fluoride laser pumped by high-energy electrons and reach the 100 MJ threshold. Others used the same data and new versions of their computer simulations to suggest that careful shaping of the laser pulse and more beams spread more evenly could achieve ignition with a laser powered between 5 and 10 MJ.
These results prompted the DOE to request a custom military ICF facility named the "Laboratory Microfusion Facility" (LMF). LMF would use a driver on the order of 10 MJ, delivering fusion yields of between 100 and 1,000 MJ. A 1989–1990 review of this concept by the National Academy of Sciences suggested that LMF was too ambitious, and that fundamental physics needed to be further explored. They recommended further experiments before attempting to move to a 10 MJ system. Nevertheless, the authors noted, "Indeed, if it did turn out that a 100 MJ driver were required for ignition and gain, one would have to rethink the entire approach to, and rationale for, ICF".
Laboratory Microfusion Facility and Nova Upgrade, 1990
As of 1992, the Laboratory Microfusion Facility was estimated to cost about $1 billion. LLNL initially submitted a design with a 5 MJ 350 nm (UV) driver that would be able to reach about 200 MJ yield, which was enough to attain the majority of the LMF goals.That program was estimated to cost about $600 million FY 1989 dollars. An additional $250 million would pay to upgrade it to a full 1,000 MJ. The total would surpass $1 billion to meet all of the goals requested by the DOE.
The NAS review led to a reevaluation of these plans, and in July 1990, LLNL responded with the Nova Upgrade, which would reuse most of Nova, along with the adjacent Shiva facility. The resulting system would be much lower power than the LMF concept, with a driver of about 1 MJ. The new design included features that advanced the state of the art in the driver section, including multi-pass in the main amplifiers, and 18 beamlines (up from 10) that were split into 288 "beamlets" as they entered the target area. The plans called for the installation of two main banks of beamlines, one in the existing Nova beamline room, and the other in the older Shiva building next door, extending through its laser bay and target area into an upgraded Nova target area. The lasers would deliver about 500 TW in a 4 ns pulse. The upgrades were expected to produce fusion yields of between 2 and 10 MJ. The initial estimates from 1992 estimated construction costs around $400 million, with construction taking place from 1995 to 1999.
NIF, 1994
Throughout this period, the ending of the Cold War led to dramatic changes in defense funding and priorities. The political support for nuclear weapons declined and arms agreements led to a reduction in warhead count and less design work. The US was faced with the prospect of losing a generation of nuclear weapon designers able to maintain existing stockpiles, or design new weapons. At the same time, the Comprehensive Nuclear-Test-Ban Treaty (CTBT) was signed in 1996, which would ban all criticality testing and made the development of newer generations of nuclear weapons more difficult.
Out of these changes came the Stockpile Stewardship and Management Program (SSMP), which, among other things, included funds for the development of methods to design and build nuclear weapons without having to test them explosively. In a series of meetings that started in 1995, an agreement formed between the labs to divide up SSMP efforts. An important part of this would be confirmation of computer models using low-yield ICF experiments. The Nova Upgrade was too small to use for these experiments. A redesign matured into NIF in 1994. The estimated cost of the project remained almost $1 billion, with completion in 2002.
In spite of the agreement, the large project cost combined with the ending of similar projects at other labs resulted in critical comments by scientists at other labs, Sandia National Laboratories in particular. In May 1997, Sandia fusion scientist Rick Spielman publicly stated that NIF had "virtually no internal peer review on the technical issues" and that "Livermore essentially picked the panel to review themselves". A retired Sandia manager, Bob Puerifoy, was even more blunt than Spielman: "NIF is worthless ... it can't be used to maintain the stockpile, period". Ray Kidder, one of the original developers of the ICF concept at LLNL, was also highly critical. He stated in 1997 that its primary purpose was to "recruit and maintain a staff of theorists and experimentalists" and that while some of the experimental data would prove useful for weapons design, differences in the experimental setup limit their relevance. "Some of the physics is the same; but the details, 'wherein the devil lies,' are quite different. It would therefore also be wrong to assume that NIF will be able to support for the long term a staff of weapons designers and engineers with detailed design competence comparable to that of those now working at the weapons design laboratories."
In 1997, Victor Reis, assistant secretary for Defense Programs within DOE and SSMP chief architect defended the program telling the U.S. House Armed Services Committee that NIF was "designed to produce, for the first time in a laboratory setting, conditions of temperature and density of matter close to those that occur in the detonation of nuclear weapons. The ability to study the behavior of matter and the transfer of energy and radiation under these conditions is key to understanding the basic physics of nuclear weapons and predicting their performance without underground nuclear testing." In 1998, two JASON panels, composed of scientific and technical experts, stated that NIF is the most scientifically valuable of all programs proposed for science-based stockpile stewardship.
Despite the initial criticism, Sandia, as well as Los Alamos, supported the development of many NIF technologies, and both laboratories later became partners with NIF in the National Ignition Campaign.
Construction of first unit, 1994–1998
Work on the NIF started with a single beamline demonstrator, Beamlet. Beamlet successfully operated between 1994 and 1997. It was then sent to Sandia National Laboratories as a light source in their Z machine. A full-sized demonstrator then followed, in AMPLAB, which started operations in 1997. The official groundbreaking on the main NIF site was on May 29, 1997.
At the time, the DOE was estimating that the NIF would cost approximately $1.1 billion and another $1 billion for related research, and would be complete as early as 2002. Later in 1997 the DOE approved an additional $100 million in funding and pushed the operational date back to 2004. As late as 1998 LLNL's public documents stated the overall price was $1.2 billion, with the first eight lasers coming online in 2001 and full completion in 2003.
The facility's physical scale alone made the construction project challenging. By the time the "conventional facility" (the shell for the laser) was complete in 2001, more than 210,000 cubic yards of soil had been excavated, more than 73,000 cubic yards of concrete had been poured, 7,600 tons of reinforcing steel rebar had been placed, and more than 5,000 tons of structural steel had been erected. To isolate the laser system from vibration, the foundation of each laser bay was made independent of the rest of the structure. Three-foot-thick, 420-foot-long and 80-foot-wide slabs required continuous concrete pours to achieve their specifications.
In November 1997, an El Niño storm dumped two inches of rain in two hours, flooding the NIF site with 200,000 gallons of water just three days before the scheduled foundation pour. The earth was so soaked that the framing for the retaining wall sank six inches, forcing the crew to disassemble and reassemble it. Construction was halted in December 1997, when 16,000-year-old mammoth bones were discovered. Paleontologists were called in to remove and preserve the bones, delaying construction by four days.
A variety of research and development, technology and engineering challenges arose, such as creating an optics fabrication capability to supply the laser glass for NIF's 7,500 meter-sized optics. State-of-the-art optics measurement, coating and finishing techniques were developed to withstand NIF's high-energy lasers, as were methods for amplifying the laser beams to the needed energy levels. Continuous-pour glass, rapid-growth crystals, innovative optical switches, and deformable mirrors were among NIF's technology innovations developed.
Sandia, with extensive experience in pulsed power delivery, designed the capacitor banks used to feed the flashlamps, completing the first unit in October 1998. To everyone's surprise, the Pulsed Power Conditioning Modules (PCMs) suffered capacitor failures that led to explosions. This required a redesign of the module to contain the debris, but since the concrete had already been poured, this left the new modules so tightly packed that in-place maintenance was impossible. Another redesign followed, this time allowing the modules to be removed from the bays for servicing. Continuing problems further delayed operations, and in September 1999, an updated DOE report stated that NIF required up to $350 million more and completion occur only in 2006.
Re-baseline and GAO report, 1999–2000
Throughout this period the problems with NIF were not reported up the management chain. In 1999 then Secretary of Energy Bill Richardson reported to Congress that NIF was on time and budget, as project leaders had reported. In August that year it was revealed that neither claim was close to the truth. As the Government Accountability Office (GAO) would later note, "Furthermore, the Laboratory's former laser director, who oversaw NIF and all other laser activities, assured Laboratory managers, DOE, the university, and the Congress that the NIF project was adequately funded and staffed and was continuing on cost and schedule, even while he was briefed on clear and growing evidence that NIF had serious problems". A DOE Task Force reported to Richardson in January 2000 that "organizations of the NIF project failed to implement program and project management procedures and processes commensurate with a major research and development project... ...no one gets a passing grade on NIF Management: not the DOE's office of Defense Programs, not the Lawrence Livermore National Laboratory and not the University of California".
Given the budget problems, the US Congress requested an independent GAO review. They returned a critical report in August 2000 estimating that the cost was likely to be $3.9 billion, including R&D, and that the facility was unlikely to be completed anywhere near on time. The report noted management problems for the overruns, and criticized the program for failing to budget money for target fabrication, including it in operational costs instead of development.
In 2000, the DOE began a comprehensive "rebaseline review" because of the technical delays and project management issues, and adjusted the schedule and budget accordingly. John Gordon, National Nuclear Security Administrator, stated "We have prepared a detailed bottom-up cost and schedule to complete the NIF project... The independent review supports our position that the NIF management team has made significant progress and resolved earlier problems". The report revised their budget estimate to $2.25 billion, not including related R&D which pushed it to $3.3 billion total, and pushed back the completion date to 2006 with the first lines coming online in 2004. A follow-up report the next year pushed the budget to $4.2 billion, and the completion date to 2008.
The project got a new management team in September 1999, headed by George Miller, who was named acting associate director for lasers. Ed Moses, former head of the Atomic Vapor Laser Isotope Separation (AVLIS) program at LLNL, became NIF project manager. Thereafter, NIF management received many positive reviews and the project met the budgets and schedules approved by Congress. In October 2010, the project was named "Project of the Year" by the Project Management Institute, which cited NIF as a "stellar example of how properly applied project management excellence can bring together global teams to deliver a project of this scale and importance efficiently."
Tests and construction completion, 2003–2009
In May 2003, the NIF achieved "first light" on a bundle of four beams, producing a 10.4 kJ IR pulse in a single beamline. In 2005 the first eight beams produced 153 kJ of IR, eclipsing OMEGA as the planet's highest energy laser (per pulse). By January 2007 all of the LRUs in the Master Oscillator Room (MOOR) were complete and the computer room had been installed. By August 2007, 96 laser lines were completed and commissioned, and "A total infrared energy of more than 2.5 megajoules has now been fired. This is more than 40 times what the Nova laser typically operated at the time it was the world's largest laser".
In 2005, an independent review by the JASON Defense Advisory Group that was generally positive, concluded that "The scientific and technical challenges in such a complex activity suggest that success in the early attempts at ignition in 2010, while possible, is unlikely". On January 26, 2009, the final line replaceable unit (LRU) was installed, unofficially completing construction. On February 26, 2009, NIF fired all 192 laser beams into the target chamber. On March 10, 2009, NIF became the first laser to break the megajoule barrier, delivering 1.1 MJ of UV light, known as 3ω (from third-harmonic generation), to the target chamber center in a shaped ignition pulse. The main laser delivered 1.952 MJ of IR.
Operations, 2009–2012
On May 29, 2009, the NIF was dedicated in a ceremony attended by thousands. The first laser shots into a hohlraum target were fired in late June.
Buildup to main experiments, 2010
On January 28, 2010, NIF reported the delivery of a 669 kJ pulse to a gold hohlraum, breaking records for laser power delivery, and analysis suggested that suspected interference by generated plasma would not be a problem in igniting a fusion reaction. Due to the size of the test hohlraums, laser/plasma interactions produced plasma-optics gratings, acting like tiny prisms, which produced symmetric X-ray drive on the capsule inside the hohlraum.
After gradually altering the wavelength of the laser, scientists compressed a spherical capsule evenly and heated it to 3.3 million kelvins (285 eV). The capsule contained cryogenically cooled gas, acting as a substitute for the deuterium and tritium fuel capsules to be used later. Plasma Physics Group Leader Siegfried Glenzer said that they could maintain the precise fuel layers needed in the lab, but not yet within the laser system.
As of January 2010, the NIF reached 1.8 megajoules. The target chamber then needed to be equipped with shields to block neutrons.
National Ignition Campaign 2010–2012
With the main construction complete, NIF started its National Ignition Campaign (NIC) to reach ignition. At the time, articles appeared in science magazines stating that ignition was imminent. Scientific American opened a 2010 review article with the statement "Ignition is close now. Within a year or two..."
The first test was carried out on October 8, 2010, at slightly over 1 MJ. However, problems slowed the drive toward ignition-level laser energies in the 1.4–1.5 MJ range.
One problem was the potential for damage from overheating due to a greater concentration of energy on optical components. Other issues included problems layering the fuel inside the target, and minute quantities of dust on the capsule surface.
The power level continued to increase and targets became more sophisticated. Then minute amounts of water vapor appeared in the target chamber and froze to the windows on the ends of the hohlraums, causing an asymmetric implosion. This was solved by adding a second layer of glass on either end, in effect creating a storm window.
Shots halted from February to April 2011, to conduct SSMP materials experiments. Then, NIF was upgraded, improving diagnostic and measurement instruments. The Advanced Radiographic Capability (ARC) system was added, which uses 4 of the NIF's 192 beams as a backlight for imaging the implosion sequence. ARC is essentially a petawatt-class laser with peak power exceeding a quadrillion (10) watts. It is designed to produce brighter, more penetrating, higher-energy x rays. ARC became the world's highest-energy short-pulse laser, capable of creating picosecond-duration laser pulses to produce energetic x rays in the range of 50–100 keV.
NIC runs restarted in May 2011 with the goal of more precisely timing the four laser shock waves that compress the fusion target.
In January 2012, Mike Dunne, director of NIF's laser fusion energy program, predicted that ignition would be achieved at NIF by October. In the same month, the NIF fired a record high 57 shots. On March 15 NIF produced a laser pulse with 411 TW of peak power. On July 5, it produced a shorter pulse of 1.85 MJ and increased power of 500 TW.
DOE Report, July 19, 2012
NIC was periodically reviewed. The 6th review, was published on July 19, 2012. The report praised the quality of the installation: lasers, optics, targets, diagnostics, and operations. However:
- The integrated conclusion based on this extensive period of experimentation, however, is that considerable hurdles must be overcome to reach ignition or the goal of observing unequivocal alpha heating. Indeed the reviewers note that given the unknowns with the present 'semi-empirical' approach, the probability of ignition before the end of December is extremely low and even the goal of demonstrating unambiguous alpha heating is challenging.
Further, the report expressed deep concerns that the gaps between observed performance and simulation codes implied that the current codes were of limited utility. Specifically, they found a lack of predictive ability of the radiation drive to the capsule and inadequately modeled laser–plasma interactions. Pressure was reaching only one half to one third of that required for ignition, far below the predicted values. The memo discussed the mixing of ablator material and capsule fuel likely due to hydrodynamics instabilities in the ablator's outer surface.
The report suggested using a thicker ablator, although this would increase its inertia. To keep the required implosion speed, they proposed that the NIF energy be increased to 2MJ. It questioned whether or not the energy was sufficient to compress a large enough capsule to avoid the mix limit and reach ignition. The report concluded that ignition within the calendar year 2012 was 'highly unlikely'.
NIC officially ended on September 30, 2012. Media reports suggested that NIF would shift its focus toward materials research.
In 2008, LLNL began the Laser Inertial Fusion Energy program (LIFE), to explore ways to use NIF technologies as the basis for a commercial power plant design. The focus was on pure fusion devices, incorporating technologies that developed in parallel with NIF that would greatly improve the performance of the design. In April 2014, LIFE ended.
Fuel gain breakeven, 2013
A NIF fusion shot on September 27, 2013, produced more energy than was absorbed by the deuterium–tritium fuel. This has been confused with having reached "scientific breakeven", defined as the fusion energy exceeding the laser input energy. Using this definition gives 14.4 kJ out and 1.8 MJ in, a ratio of 0.008.
Stockpile experiments, 2013–2015
In 2013, NIF shifted focus to materials and weapons research. Experiments beginning in FY 2015 used plutonium targets. Plutonium shots simulate the compression of the primary in a nuclear bomb by high explosives, which had not seen direct testing since CNTB took effect. Plutonium use ranged from less than a milligram to 10 milligrams.
In FY 2014, NIF performed 191 shots, slightly more than one every two days. As of April 2015 NIF was on track to meet its goal of 300 laser shots in FY 2015.
Back to fusion, 2016–present
On January 28, 2016, NIF successfully executed its first gas pipe experiment intended to study the absorption of large amounts of laser light within 1 centimetre (0.39 in) long targets relevant to high-gain magnetized liner inertial fusion (MagLIF). In order to investigate key aspects of the propagation, stability, and efficiency of laser energy coupling at full scale for high-gain MagLIF target designs, a single quad of NIF was used to deliver 30 kJ of energy to a target during a 13 nanosecond shaped pulse. Data return was favorable.
In 2018, improvements in controlling compression asymmetry was demonstrated in a shot with an output of 1.9×10 neutrons, resulting in 0.054 MJ of fusion energy released by a 1.5 MJ laser pulse.
Burning plasma achieved, 2021
Experiments in 2020 and 2021 yielded the world's first burning plasmas, in which most of the plasma heating came from nuclear fusion reactions. This result was followed on August 8, 2021 by the world's first ignited plasma, in which the fusion heating was sufficient to sustain the thermonuclear reaction. It produced excess neutrons consistent with a short-lived chain reaction of around 100 trillionths of a second.
The fusion energy yield of the 2021 experiment was estimated to be 70% of the laser energy incident on the plasma. This result slightly beat the former record of 67% set by the JET torus in 1997. Taking the energy efficiency of the laser itself into account, the experiment used about 477 MJ of electrical energy to get 1.8 MJ of energy into the target to create 1.3 MJ of fusion energy.
Several design changes enabled this result. The material of the capsule shell was changed to diamond to increase the absorbance of secondary x-rays created by the laser burst, thus increasing the efficacy of the collapse, and its surface was further smoothed. The size of the hole in the capsule used to inject fuel was reduced. The holes in the gold cylinder surrounding the capsule were shrunk to reduce energy loss. The laser pulse was extended.
Scientific breakeven achieved, 2022
This section appears to contradict itself on the amount of energy produced by the first scientific breakeven. Please see the talk page for more information. (May 2024) |
The NIF became the first fusion experiment to achieve scientific breakeven on December 5, 2022, with an experiment producing 3.15 megajoules of energy from a 2.05 megajoule input of laser light for an energy gain of about 1.5. Charging the laser consumed "well above 400 megajoules". In a public announcement on December 13, the Secretary of Energy Jennifer Granholm announced the facility had achieved ignition. While this was often characterized as a "net energy gain" from fusion, this was only true with respect to the energy delivered by the laser; reports sometimes omitted the ~300 MJ power input required.
The feat required the use of a slightly thicker and smoother capsule surrounding the fuel and a 2.05 MJ laser (up from 1.9 MJ in 2021), yielding 3.15 MJ, a 54% surplus. They also redistributed the energy among the split laser beams, which produced a more symmetrical (spherical) implosion.
The NIF achieved breakeven for a second time on July 30, 2023 yielding 3.88 MJ, an 89% surplus. At least four of six shots performed after the first successful one in December 2022 achieved breakeven. These successes led the DOE to fund three additional research centers. Lawrence Livermore planned to raise laser energy to 2.2 MJ per shot through upgraded optics and lasers c. 2023, reaching it on the experiment held on October 30, 2023.
Similar projects
Some similar experimental ICF projects are:
- Laser Mégajoule (LMJ)
- Nike laser
- High Power laser Energy Research facility (HiPER)
- Laboratory for Laser Energetics (LLE)
- Magnetized liner inertial fusion (MagLIF)
- Shenguang-II High Power Laser
Pictures
- Viewing port allows a look into the interior of the 30 foot diameter target chamber.
- Exterior view of the upper third of the target chamber. The large square beam ports are prominent.
- A technician loads an instrument canister into the vacuum-sealed diagnostic instrument manipulator.
- The flashlamps used to pump the main amplifiers are the largest ever in commercial production.
- The glass slabs used in the amplifiers are likewise much larger than those used in previous lasers.
In popular culture
The NIF was used as the set for the starship Enterprise's warp core in the 2013 movie Star Trek Into Darkness.
See also
- Z Pulsed Power Facility
- Chain reaction
- HiPER
- Inertial confinement fusion
- ITER
- Laser Mégajoule
- Nuclear fusion
- Nuclear reactor
Notes
- It is not clearly stated why Nova Upgrade would be too small for SSMP, no reason is given in the available resources.
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{{cite web}}
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External links
- "National Ignition Facility: How NIF Works, NIF & Photon Science". May 27, 2010. Archived from the original on May 27, 2010. Retrieved December 5, 2020.
- "Lasers, Photonics, and Fusion Science: Science and Technology on a Mission". lasers.llnl.gov. Retrieved December 5, 2020.
- "NIF Director, Dr Ed Moses, on the progress of the facility". Ingenia. December 2007. Archived from the original on October 2, 2011. Retrieved December 5, 2020.
- "NIF project director Moses says facility is ready to go". spie.org. Retrieved December 5, 2020.
- "Inside Livermore Lab's Race to Invent Clean Energy". Newsweek. November 13, 2009. Retrieved December 5, 2020.
- Eric (April 10, 2011). "NIF Laser Fusion in Fulldome". Retrieved December 5, 2020.
- Clery, Daniel (November 23, 2020). "Laser fusion reactor approaches 'burning plasma' milestone". Science. 370 (6520): 1019–1020. Bibcode:2020Sci...370.1019C. doi:10.1126/science.370.6520.1019. PMID 33243866. S2CID 227182275. Retrieved December 5, 2020.
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