Cf 252 spontaneous fission rate8/10/2023 ![]() Nuclear fission within a reactor, produces many neutrons and can be used for a variety of purposes including power generation and experiments. In addition, electrons of energy over about 50 MeV may induce giant dipole resonance in nuclides by a mechanism which is the inverse of internal conversion, and thus produce neutrons by a mechanism similar to that of photoneutrons. Typically photons begin to produce neutrons on interaction with normal matter at energies of about 7 to 40 MeV, which means that radiotherapy facilities using megavoltage X-rays also produce neutrons, and some require neutron shielding. The number of neutrons released by each fission event is dependent on the substance. Neutrons are produced when photons above the nuclear binding energy of a substance are incident on that substance, causing it to undergo giant dipole resonance after which it either emits a neutron ( photoneutron) or undergoes fission ( photofission). High-energy bremsstrahlung photoneutron/photofission systems Typically these accelerators operate with energies in the > 1 MeV range. Traditional particle accelerators with hydrogen (H), deuterium (D), or tritium (T) ion sources may be used to produce neutrons using targets of deuterium, tritium, lithium, beryllium, and other low-Z materials. Various applications from a hobby enthusiast scene up to commercial applications have developed, mostly in the US. Inertial electrostatic confinement devices such as the Farnsworth-Hirsch fusor use an electric field to heat a plasma to fusion conditions and produce neutrons. The dense plasma focus neutron source produces controlled nuclear fusion by creating a dense plasma within which heats ionized deuterium and/or tritium gas to temperatures sufficient for creating fusion. Medium-sized devices Plasma focus and plasma pinch devices Some accelerator-based neutron generators induce fusion between beams of deuterium and/or tritium ions and metal hydride targets which also contain these isotopes. 2 H ( deuterium) + >2.26 MeV photon → 1 neutron + 1H.9 Be + >1.7 MeV photon → 1 neutron + 2 4He.Gamma radiation with an energy exceeding the neutron binding energy of a nucleus can eject a neutron ( photoneutron). Radioisotopes which decay with high-energy photons co-located with beryllium or deuterium Usual combinations of materials are plutonium- beryllium (PuBe), americium-beryllium (AmBe), or americium- lithium (AmLi). The size and cost of these neutron sources are comparable to spontaneous fission sources. The useful lifetime for such sources depends on the half-life of the radioisotope. An alpha-beryllium neutron source may produce about 30 neutrons per 10 6 alpha particles. Alpha neutron sources typically produce ~10 6–10 8 neutrons per second. Thus, one can make a neutron source by mixing an alpha-emitter such as radium, polonium, or americium with a low-atomic-weight isotope, usually by blending powders of the two materials. Neutrons are produced when alpha particles hit any of several light isotopes including isotopes of beryllium, carbon, or oxygen. Radioisotopes which alpha decay mixed with a light element A typical 252Cf neutron source emits 10 7 to 10 9 neutrons per second when new but with a half-life of 2.6 years, neutron output drops by half in 2.6 years. 252Cf neutron sources are typically 1/4" to 1/2" in diameter and 1" to 2" in length. 252Cf and all other SF neutron sources are made by irradiating uranium or a transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into the SF isotope. The most common spontaneous fission source is the isotope californium-252. Some isotopes undergo SF with emission of neutrons. Neutron source variables include the energy of the neutrons emitted by the source, the rate of neutrons emitted by the source, the size of the source, the cost of owning and maintaining the source, and government regulations related to the source. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear power. Fundamental research with neutrons: Ultracold neutrons Ī neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons.For neutron sources used in nuclear weapons, see modulated neutron initiator. ![]()
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