Physics and Engineering of Radiation Detection

2.6. Interaction of Neutral Particles with Matter 137

Analytic Function

Air

Water

Figure 2.5.8: Variation of elec-

tron range ing/cm^2 with energy in

MeVcomputed from the equations

2.5.28. Also shown are the ESTAR

values for air and water.

2.6 InteractionofNeutralParticleswithMatter..............

Neutrons and neutrinos are two chargeless particles that are found in abundance in
nature. As neutrons have been found to be extremely useful, we will discuss here
how they interact with matter in detail. The interaction mechanisms of neutrinos
will be discussed briefly afterward.

2.6.A Neutrons

Since neutrons do not carry any electrical charge, they are not affected by the electric
field of the atoms. This enables them to move swiftly through large open atomic
spaces without interacting with atoms. However if they pass near the nuclei they
encounter strong nuclear force. In such a situation, depending on their energy, they
can interact with the nuclei in the following ways,

Elastic scattering

Inelastic scattering

Spallation reaction

Transmutation

Radiative capture