Spallation neutron sources for neutron beam research

The major components of a spallation neutron source for neutron beam research are: an accelerator to produce intense bursts of energetic particles such as protons of 800 MeV; a target of a heavy material thick enough to absorb the majority of the energy of bombarding particles; an assembly of moderators and reflectors to slow the neutrons produced in the heavy target to thermal energies and a biological shield with beam holes left to allow bursts of neutrons to emerge from the moderator. Neutron beam instruments designed to use time of flight techniques for determining the neutron energy are placed in the neutron beams. The article illustrates the general principles by reference to the design of the spallation source being constructed at the Rutherford Laboratory.