Page 24 - bukuneutron

1.6.1 Neutron slowing down

Fast neutron travels at very high speed with a high ki-
netic energy ranges within MeV. The neutron can be
slow down to low energy at eV ranges. The Neutron
within these energy ranges are classified as thermal
and epi-thermal neutron. Slow down of neutron speed
is known as a moderation process, where it is actually
a collision of neutron with the nucleus of atom in a mod-
erator material. Collision of neutron with the target nu-
cleus happen in elastic and inelastic manner. The col-
lision will scatter neutron into various directions. The
scattering of neutron happened in elastic or in inelas-
tic manner. The energy of neutron remain the same
in elastic scattering where as some reduction in neu-
tron energy resulting from inelastic scattering. Ther-
mal neutron from sealed source, spallation machine
or research reactor are widely used for many applica-
tions. The capability of collision for each material is
depending on the neutron cross section value. The
higher cross section value of material gives the higher
probability of interaction with neutron.

Elastic Scattering Figure 1.7 illustrates the process
of elastic scattering of a neutron off a target nucleus.
In the elastic scattering reaction, the conservation of
momentum and kinetic energy is represented by the
Equation 1.1 and Equation 1.2. Conservation of mo-
mentum (mv)Conservation of kinetic energy where: m=mass
of the neutronnm=mass of the target nucleus Tv=initial

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