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			{{short description\|Ionizing radiation}}{{More citations needed\|date=September 2024}}] consists of ] nuclei and is readily stopped by a sheet of paper. ], consisting of ] or ]s, is stopped by a thin aluminum plate, but ] requires shielding by dense material such as lead or concrete.<ref name=NRC_Radiation>{{cite web \|url=https://www.nrc.gov/about-nrc/radiation/health-effects/radiation-basics.html \|title=Radiation Basics \|date=2017-10-02 \|publisher=United States Nuclear Regulatory Com}}</ref>]]
	'''Beta particles''' are high-energy ]s or ]s emitted by certain types of ] ] such as ]-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed ]. They are designated by the ] beta (β).

			A '''beta particle''', also called '''beta ray''' or '''beta radiation''' (symbol '''β'''), is a high-energy, high-speed ] or ] emitted by the ] of an ], known as ]. There are two forms of beta decay, β<sup>−</sup> decay and β<sup>+</sup> decay, which produce electrons and positrons, respectively.<ref>{{cite web \|title=Beta Decay \|url=http://www.lbl.gov/abc/wallchart/chapters/03/2.html \|work=Nuclear Wall Chart \|author=Lawrence Berkeley National Laboratory \|publisher=] \|date=9 August 2000 \|access-date=17 January 2016 \|archive-date=3 March 2016 \|archive-url=https://web.archive.org/web/20160303195332/http://www2.lbl.gov/abc/wallchart/chapters/03/2.html \|url-status=dead}}</ref>
	There are two forms of beta decay, β<sup>−</sup> and β<sup>+</sup>, which respectively give rise to the electron and the ].

			Beta particles with an energy of 0.5 MeV have a range of about one metre in the air; the distance is dependent on the particle's energy and the air's ] and composition.
	==β<sup>−</sup> decay (electron)==

			Beta particles are a type of ], and for ] purposes, they are regarded as being more ionising than ]s, but less ionising than ]s.<!--This is the correct ordering. If you believe otherwise, please cite a reliable source, or discuss on the Talk page.--> The higher the ionising effect, the greater the damage to living tissue, but also the lower the ] of the radiation through matter.
	Unstable atomic nuclei with an excess of neutrons may undergo β<sup>−</sup> decay, where a ] is converted into a ], an electron and an electron-type antineutrino (the ] of the ]):

			==Beta decay modes==
	<math>\mbox{n} \rightarrow \mbox{p} + \mbox{e}^- + \bar{\nu}_{e}</math>

			=== β<sup>−</sup> decay (electron emission) ===
	The electron and the antineutrino are emitted from the nucleus.
			{{main\|Beta_decay#.CE.B2.E2.88.92_decay\|l1=β<sup>−</sup> decay}}
			]. An antineutrino (not shown) is always emitted along with an electron. Insert: in the decay of a free neutron, a proton, an electron (negative beta ray), and an ] are produced.]]

			An unstable atomic nucleus with an excess of ]s may undergo β<sup>−</sup> decay, where a neutron is converted into a ], an electron, and an ] (the ] of the ]):
	==β<sup>+</sup> decay (positron)==

			:{{SubatomicParticle\|neutron}} → {{SubatomicParticle\|proton}} + {{SubatomicParticle\|electron}} + {{SubatomicParticle\|electron antineutrino}}
	Unstable nuclei that are deficient in neutrons may undergo β<sup>+</sup> decay, where a proton is converted into a neutron. The proton consists of two up quarks and a down quark, one of the proton's up quarks decays to a down quark, doing so, it will emit a W particle, which is unstable and decays further into a positron and an electron neutrino:

			This process is mediated by the ]. The neutron turns into a proton through the emission of a ] ]. At the ] level, W<sup>−</sup> emission turns a down quark into an up quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark).
	<math>\mbox{p} \rightarrow \mbox{n} + \mbox{e}^+ + \nu_{e}</math>
			The virtual W<sup>−</sup> boson then decays into an electron and an antineutrino.

			β− decay commonly occurs among the neutron-rich ] produced in ]s. Free neutrons also decay via this process. Both of these processes contribute to the copious quantities of beta rays and electron antineutrinos produced by fission-reactor fuel rods.
	The positron and the neutrino are emitted from the nucleus.

			=== β<sup>+</sup> decay (positron emission) ===
	<math>\mbox{p(uud)} \rightarrow \mbox{n(udd)} + \mbox{W}^+ \rightarrow \mbox{e}^+ + \nu_{e}</math>
			{{main\|Positron emission}}
			Unstable atomic nuclei with an excess of protons may undergo β<sup>+</sup> decay, also called positron decay, where a proton is converted into a neutron, a ], and an ]:

			:{{SubatomicParticle\|proton}} → {{SubatomicParticle\|neutron}} + {{SubatomicParticle\|positron}} + {{SubatomicParticle\|electron neutrino}}
	==The neutrino and conservation of energy==

			Beta-plus decay can only happen inside nuclei when the absolute value of the ] of the daughter nucleus is greater than that of the parent nucleus, i.e., the daughter nucleus is a lower-energy state.
	Due to the presence of the neutrino, the atom and the beta particle do not usually ] in opposite directions. This observation led ] to postulate the existence of neutrinos in order to prevent violation of conservation of ] and ] laws. Beta decay is mediated by the ].

			===Beta decay schemes===
	Beta particles may be stopped by a few milimeters of ]. A beta particle's flight is ten times farther than an alpha particle, as it ionizes a tenth less than an alpha particle.
			]
			The accompanying decay scheme diagram shows the beta decay of ]. <sup>137</sup>Cs is noted for a characteristic gamma peak at 661 keV, but this is actually emitted by the daughter radionuclide <sup>137m</sup>Ba. The diagram shows the type and energy of the emitted radiation, its relative abundance, and the daughter nuclides after decay.

			] is a beta emitter widely used in medicine. It has a short half-life of 14.29 days<ref name="LNHB">{{cite web \|title=Phosphorus-32 \|url=http://www.nucleide.org/DDEP_WG/Nuclides/P-32_tables.pdf \|url-status=live \|archive-url=https://ghostarchive.org/archive/20221009/http://www.nucleide.org/DDEP_WG/Nuclides/P-32_tables.pdf \|archive-date=2022-10-09 \|access-date=28 June 2022 \|website=nucleide.org \|publisher=Laboratoire Nationale Henri Bequerel}}</ref> and decays into sulfur-32 by ] as shown in this nuclear equation:
	==See also==
			:{\| border="0"
	*]
			\|- style="height:2em;"
	*]
			\|{{nuclide\|Phosphorus\|32}} \|\|→ \|\|{{nuclide\|Sulfur\|32\|charge=1+}} \|\|+ \|\|{{SubatomicParticle\|link=yes\|Electron}} \|\|+ \|\|{{SubatomicParticle\|link=yes\|Electron Antineutrino}}
	*]
			\|}
	*]
			1.709 ] of energy is released during the decay.<ref name="LNHB"/> The kinetic energy of the ] varies with an average of approximately 0.5 MeV and the remainder of the energy is carried by the nearly undetectable ]. In comparison to other beta radiation-emitting nuclides, the electron is moderately energetic. It is blocked by around 1 m of air or 5 mm of ].
	*]
	*]
	* rays: ] — ] — ] — ] — ]

			== Interaction with other matter ==
	]

			] light being emitted from a ] reactor pool is due to high-speed beta particles traveling faster than the speed of light (]) in water (which is 75% of the speed of light in vacuum).]]Of the three common types of radiation given off by radioactive materials, ], beta and ], beta has the medium penetrating power and the medium ionising power. Although the beta particles given off by different radioactive materials vary in energy, most beta particles can be stopped by a few millimeters of ]. However, this does not mean that beta-emitting isotopes can be completely shielded by such thin shields: as they decelerate in matter, beta electrons emit secondary gamma rays, which are more penetrating than betas per se. Shielding composed of materials with lower atomic weight generates gammas with lower energy, making such shields somewhat more effective per unit mass than ones made of larger atoms such as lead.
	]

	]
			Being composed of charged particles, beta radiation is more strongly ionizing than gamma radiation. When passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off ] ]s.
	]

	]
			In water, beta radiation from many ]s typically exceeds the speed of light in that material (which is about 75% that of light in vacuum),<ref>The macroscopic speed of light in water is 75% of the speed of light in vacuum (called ''c''). The beta particle is moving faster than 0.75 c, but not faster than c.</ref> and thus generates blue ] when it passes through water. The intense beta radiation from the fuel rods of ]s can thus be visualized through the transparent water that covers and shields the reactor (see illustration at right).
	]

	]
			=== Detection and measurement ===
	]
			] (after insertion of an artificial source ])]]
	]
			The ionizing or excitation effects of beta particles on matter are the fundamental processes by which radiometric detection instruments detect and measure beta radiation. The ionization of gas is used in ] and ], and the excitation of ]s is used in ]s.
	]
			The following table shows radiation quantities in SI and non-SI units:
	]
			{{Radiation related quantities}}
	]

	]
			* The ] (Gy) is the SI unit of ], which is the amount of radiation energy deposited in the irradiated material. For beta radiation this is numerically equal to the ] measured by the ], which indicates the stochastic biological effect of low levels of radiation on human tissue. The radiation weighting conversion factor from absorbed dose to equivalent dose is 1 for beta, whereas alpha particles have a factor of 20, reflecting their greater ionising effect on tissue.
	]
			* The ] is the deprecated ] unit for absorbed dose and the ] is the deprecated ] unit of equivalent dose, used mainly in the USA.
	]

			=== Beta spectroscopy ===
			The energy contained within individual beta particles is measured via ''beta spectrometry''; the study of the obtained distribution of energies as a ] is ''beta spectroscopy''. Determination of this energy is done by measuring the amount of deflection of the electron's path under a magnetic field.<ref>{{cite web \|last1=Boeglin \|first1=Werner \|title=4. Beta Spectroscopy — Modern Lab Experiments documentation \|url=https://wanda.fiu.edu/boeglinw/courses/Modern_lab_manual3/beta_spectroscopy.html \|website=wanda.fiu.edu}}</ref>

			== Applications ==
			Beta particles can be used to treat health conditions such as ] and ] and are also used as tracers. ] is the material most commonly used to produce beta particles.

			Beta particles are also used in quality control to test the thickness of an item, such as ], coming through a system of rollers. Some of the beta radiation is absorbed while passing through the product. If the product is made too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the manufactured paper will then move the rollers to change the thickness of the final product.

			An illumination device called a '']'' contains ] and a ]. As tritium ], it emits beta particles; these strike the phosphor, causing the phosphor to give off ]s, much like the ] in a television. The illumination requires no external power, and will continue as long as the tritium exists (and the phosphors do not themselves chemically change); the ] will drop to half its original value in 12.32 years, the ] of tritium.

			Beta-plus (or ]) decay of a ] ] is the source of the positrons used in ] (PET scan).

			== History ==
			], while experimenting with ], accidentally found out that ] exposed a ] plate, wrapped with black paper, with some unknown ] that could not be turned off like ]s.

			] continued these experiments and discovered two different kinds of radiation:

			* ] that did not show up on the Becquerel plates because they were easily absorbed by the black wrapping paper
			* beta particles which are 100 times more penetrating than alpha particles.

			He published his results in 1899.<ref>{{cite journal \|author=E. Rutherford \|url=https://books.google.com/books?id=ipMOAAAAIAAJ&pg=PA109 \|title=Uranium radiation and the electrical conduction produced by it \|journal=Philosophical Magazine \|volume=47 \|issue=284 \|pages=109–163 \|doi=10.1080/14786449908621245 \|date=8 May 2009 \|orig-year=Paper published by Rutherford in 1899}}</ref>

			In 1900, Becquerel measured the ] ({{math\|''m''/''e''}}) for beta particles by the method of ] used to study cathode rays and identify the electron. He found that {{math\|''e''/''m''}} for a beta particle is the same as for Thomson's electron, and therefore suggested that the beta particle is in fact an electron.

			== Health ==
			Beta particles are moderately penetrating in living tissue, and can cause spontaneous ] in ].

			Beta sources can be used in ] to kill cancer cells.

			== See also ==
			* ]
			* ]
			* ]
			* ]
			* ]

			== References ==
			{{reflist}}

			== Further reading ==
			* <!-- some company going out of business? -->
			* University of Virginia Lecture
			* {{Webarchive\|url=https://web.archive.org/web/20170506071143/http://www.physics.isu.edu/radinf/hist.htm \|date=2017-05-06 }} at Idaho State University
			* {{Webarchive\|url=https://web.archive.org/web/20061205215708/http://www.lbl.gov/abc/Basic.html \|date=2006-12-05 }} at the Lawrence Berkeley National Laboratory

			{{Radiation}}

			{{Authority control}}

			]
			]

Latest revision as of 15:16, 13 September 2024

Ionizing radiation

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A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus, known as beta decay. There are two forms of beta decay, β decay and β decay, which produce electrons and positrons, respectively.

Beta particles with an energy of 0.5 MeV have a range of about one metre in the air; the distance is dependent on the particle's energy and the air's density and composition.

Beta particles are a type of ionizing radiation, and for radiation protection purposes, they are regarded as being more ionising than gamma rays, but less ionising than alpha particles. The higher the ionising effect, the greater the damage to living tissue, but also the lower the penetrating power of the radiation through matter.

Beta decay modes

β decay (electron emission)

Main article: β decay

An unstable atomic nucleus with an excess of neutrons may undergo β decay, where a neutron is converted into a proton, an electron, and an electron antineutrino (the antiparticle of the neutrino):

n
→
p
+
e
+
ν
_e

This process is mediated by the weak interaction. The neutron turns into a proton through the emission of a virtual W boson. At the quark level, W emission turns a down quark into an up quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark). The virtual W boson then decays into an electron and an antineutrino.

β− decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors. Free neutrons also decay via this process. Both of these processes contribute to the copious quantities of beta rays and electron antineutrinos produced by fission-reactor fuel rods.

β decay (positron emission)

Main article: Positron emission

Unstable atomic nuclei with an excess of protons may undergo β decay, also called positron decay, where a proton is converted into a neutron, a positron, and an electron neutrino:

p
→
n
+
e
+
ν
_e

Beta-plus decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is greater than that of the parent nucleus, i.e., the daughter nucleus is a lower-energy state.

Beta decay schemes

Caesium-137 decay scheme, showing it initially undergoes beta decay. The 661 keV gamma peak associated with Cs is actually emitted by the daughter radionuclide.

The accompanying decay scheme diagram shows the beta decay of caesium-137. Cs is noted for a characteristic gamma peak at 661 keV, but this is actually emitted by the daughter radionuclide Ba. The diagram shows the type and energy of the emitted radiation, its relative abundance, and the daughter nuclides after decay.

Phosphorus-32 is a beta emitter widely used in medicine. It has a short half-life of 14.29 days and decays into sulfur-32 by beta decay as shown in this nuclear equation:

₁₅P

→

₁₆S

ν
_e

1.709 MeV of energy is released during the decay. The kinetic energy of the electron varies with an average of approximately 0.5 MeV and the remainder of the energy is carried by the nearly undetectable electron antineutrino. In comparison to other beta radiation-emitting nuclides, the electron is moderately energetic. It is blocked by around 1 m of air or 5 mm of acrylic glass.

Interaction with other matter

Blue Cherenkov radiation light being emitted from a TRIGA reactor pool is due to high-speed beta particles traveling faster than the speed of light (phase velocity) in water (which is 75% of the speed of light in vacuum).

Of the three common types of radiation given off by radioactive materials, alpha, beta and gamma, beta has the medium penetrating power and the medium ionising power. Although the beta particles given off by different radioactive materials vary in energy, most beta particles can be stopped by a few millimeters of aluminium. However, this does not mean that beta-emitting isotopes can be completely shielded by such thin shields: as they decelerate in matter, beta electrons emit secondary gamma rays, which are more penetrating than betas per se. Shielding composed of materials with lower atomic weight generates gammas with lower energy, making such shields somewhat more effective per unit mass than ones made of larger atoms such as lead.

Being composed of charged particles, beta radiation is more strongly ionizing than gamma radiation. When passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off bremsstrahlung X-rays.

In water, beta radiation from many nuclear fission products typically exceeds the speed of light in that material (which is about 75% that of light in vacuum), and thus generates blue Cherenkov radiation when it passes through water. The intense beta radiation from the fuel rods of swimming pool reactors can thus be visualized through the transparent water that covers and shields the reactor (see illustration at right).

Detection and measurement

The ionizing or excitation effects of beta particles on matter are the fundamental processes by which radiometric detection instruments detect and measure beta radiation. The ionization of gas is used in ion chambers and Geiger–Müller counters, and the excitation of scintillators is used in scintillation counters. The following table shows radiation quantities in SI and non-SI units:

Ionizing radiation related quantities
view
talk
edit
Quantity	Unit	Symbol	Derivation	Year	SI equivalent
Activity (A)	becquerel	Bq	s	1974	SI unit
	curie	Ci	3.7×10 s	1953	3.7×10 Bq
	rutherford	Rd	10 s	1946	1000000 Bq
Exposure (X)	coulomb per kilogram	C/kg	C⋅kg of air	1974	SI unit
Exposure (X)	röntgen	R	esu / 0.001293 g of air	1928	2.58×10 C/kg
Absorbed dose (D)	gray	Gy	J⋅kg	1974	SI unit
	erg per gram	erg/g	erg⋅g	1950	1.0×10 Gy
	rad	rad	100 erg⋅g	1953	0.010 Gy
Equivalent dose (H)	sievert	Sv	J⋅kg × W_R	1977	SI unit
Equivalent dose (H)	röntgen equivalent man	rem	100 erg⋅g × W_R	1971	0.010 Sv
Effective dose (E)	sievert	Sv	J⋅kg × W_R × W_T	1977	SI unit
Effective dose (E)	röntgen equivalent man	rem	100 erg⋅g × W_R × W_T	1971	0.010 Sv

The gray (Gy) is the SI unit of absorbed dose, which is the amount of radiation energy deposited in the irradiated material. For beta radiation this is numerically equal to the equivalent dose measured by the sievert, which indicates the stochastic biological effect of low levels of radiation on human tissue. The radiation weighting conversion factor from absorbed dose to equivalent dose is 1 for beta, whereas alpha particles have a factor of 20, reflecting their greater ionising effect on tissue.
The rad is the deprecated CGS unit for absorbed dose and the rem is the deprecated CGS unit of equivalent dose, used mainly in the USA.

Beta spectroscopy

The energy contained within individual beta particles is measured via beta spectrometry; the study of the obtained distribution of energies as a spectrum is beta spectroscopy. Determination of this energy is done by measuring the amount of deflection of the electron's path under a magnetic field.

Applications

Beta particles can be used to treat health conditions such as eye and bone cancer and are also used as tracers. Strontium-90 is the material most commonly used to produce beta particles.

Beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the beta radiation is absorbed while passing through the product. If the product is made too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the manufactured paper will then move the rollers to change the thickness of the final product.

An illumination device called a betalight contains tritium and a phosphor. As tritium decays, it emits beta particles; these strike the phosphor, causing the phosphor to give off photons, much like the cathode-ray tube in a television. The illumination requires no external power, and will continue as long as the tritium exists (and the phosphors do not themselves chemically change); the amount of light produced will drop to half its original value in 12.32 years, the half-life of tritium.

Beta-plus (or positron) decay of a radioactive tracer isotope is the source of the positrons used in positron emission tomography (PET scan).

History

Henri Becquerel, while experimenting with fluorescence, accidentally found out that uranium exposed a photographic plate, wrapped with black paper, with some unknown radiation that could not be turned off like X-rays.

Ernest Rutherford continued these experiments and discovered two different kinds of radiation:

alpha particles that did not show up on the Becquerel plates because they were easily absorbed by the black wrapping paper
beta particles which are 100 times more penetrating than alpha particles.

He published his results in 1899.

In 1900, Becquerel measured the mass-to-charge ratio (m/e) for beta particles by the method of J. J. Thomson used to study cathode rays and identify the electron. He found that e/m for a beta particle is the same as for Thomson's electron, and therefore suggested that the beta particle is in fact an electron.

Health

Beta particles are moderately penetrating in living tissue, and can cause spontaneous mutation in DNA.

Beta sources can be used in radiation therapy to kill cancer cells.

References

"Radiation Basics". United States Nuclear Regulatory Com. 2017-10-02.
Lawrence Berkeley National Laboratory (9 August 2000). "Beta Decay". Nuclear Wall Chart. United States Department of Energy. Archived from the original on 3 March 2016. Retrieved 17 January 2016.
^ "Phosphorus-32" (PDF). nucleide.org. Laboratoire Nationale Henri Bequerel. Archived (PDF) from the original on 2022-10-09. Retrieved 28 June 2022.
The macroscopic speed of light in water is 75% of the speed of light in vacuum (called c). The beta particle is moving faster than 0.75 c, but not faster than c.
Boeglin, Werner. "4. Beta Spectroscopy — Modern Lab Experiments documentation". wanda.fiu.edu.
E. Rutherford (8 May 2009) . "Uranium radiation and the electrical conduction produced by it". Philosophical Magazine. 47 (284): 109–163. doi:10.1080/14786449908621245.