Page 38 - bukuneutron
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pled to electronic module interface with the controller
and data acquisition system. Typical layout of back-
scattered gauge is illustrated in Figure 2.1.
Figure 2.1: Principle of neutron backscatterred tech-
nique.
Sealed neutron source is packed in the hydroge-
nous material such as polyethylene in which the ther-
mal neutron is obtained from thermalisation of fast neu-
tron. There are two widely used neutron source in
back-scattered technique such as the californium-252
(Cf-252) and americium-beryllium (AmBe-241). These
sealed source usually emitting majority of fast neutron,
so thermalization is required to produce thermal neu-
tron. Both are mainly emitting fast neutrons with small
fraction of thermal neutrons. Figure 2.2 shows the en-
ergy spectrum of fission neutron from Cf-252 sealed
source before and after thermalization by 15- cm of
water.
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