Neutron source

A neutron source is a device, used in solid state physics (see neutron diffraction), particle physics and to start nuclear chain reactions, that emits neutrons.

There are several kinds of neutron sources:

Small devices

• Neutrons can be generated by mixing beryllium and an alpha emitter such as radium or polonium. Neutrons are liberated when beryllium is hit by alpha particles at about 30 neutrons/million alpha particles.

• Certain isotopes undergo spontaneous fission with emission of neutrons. Californium 252 can be used this way as it decays with a conveniently intermediate half-life time of 2.65 years. To produce such an isotope, one needs a high flux nuclear reactor.

• The Farnsworth-Hirsch fusor can produce controlled nuclear fusion (at a net energy loss) and is sold commercially as a neutron source.

Large devices

• Nuclear fission in a reactor produces neutrons which can be used for experiments. This (and not the study of nuclear fission itself) is the purpose of nuclear research reactors .

• A spallation source is a high-flux source, in which protons that have been accelerator to high energies, hit a target material, prompting the emission of neutrons.

See also

• radioactive decay
• fast neutron
• slow neutron
• neutron moderator
• nuclear fission
• radioactivity