Neutron Scattering

Hot neutrons in reactors are obtained from hot sources at temperatures around 2000K .
Thermal neutrons evolve from ambient moderators while cold neutrons are obtained from
mainly liquid hydrogen or deuterium moderators . The velocity distribution of the neutrons
evolving from such a moderator are given by a Maxwell velocity distribution
o (u ) = vs exp
(2 .4)
Thereby, 0(u) du is the number of neutrons which are emitted through an unit area per
second with velocities between v and v+dv. Fig .2 .4 displays Maxwellian flux distributions
for the three types of moderators discussed above .
ulkm s - '
Figure 2 .4 :
Velocity distributions of neutrons from cold (25K), thermal (300K) and hot
(2000K) moderators .
Finally, Neutrons as well as X-rays are used for scattering experiments on materials . Table
2 .1 compares the most important properties ofboth radiations .
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