• natural sources of neutrons
– only radioactive elements, e.g. uranium
– neutron outside the nucleus will disappear after 18 minutes!
• artificial processes which produce neutrons
– (1) nuclear fission: sustained reaction of radioactive elements, e.g. uranium
– (2) spallation: disintegration of heavy elements, e.g. tantalum
• artificial sources of neutrons
– (1) nuclear reactor source: e.g. ILL laboratory in France
– (2) spallation source: e.g. ISIS laboratory in UK