Gamma ray interaction with matter

The detail of the manner in which gamma-rays interact with matter determines the size of the detector signal for... 

Gamma rays interact with matter in three ways photoe1ectr1C effect, Compton effect or scattering, and pair production. 

FIGURE 14 The relative importance of the major processes by which gamma rays interact with matter as a function of photon energy for elements of varying atomic number Z. (Adapted from Evans, R. D. (1995). The Atomic Nucleus, Copyright 1955, McGraw-Hill, by permission.)... 

Each of the types of radiation has a characteristic way of interacting with matter and transferring its energy. Alpha radiation has the least penetrating power and its effects are limited to the surface layers of a material, so it only needs to be considered when a surface is contaminated by an alpha emitter. Beta radiation has a range of up to a centimetre or two whilst X-ray, gamma... 

Particle detectors are instruments designed for the detection and measurement of sub-atomic particles such as those emitted by radioactive materials, produced by particle accelerators or observed in cosmic rays. They include electrons, protons, neutrons, alpha particles, gamma rays and numerous mesons and baryons. Most detectors utilize in some way the ionization produced when these particles interact with matter. 

The interaction of neutrons with matter is quite different from that of either charged particles or gamma rays. Depending on their energy, neutrons interact with matter by various processes. 

Neutrons and gammas have no charge. They interact with matter in ways that will be discussed below, but there is a finite nonzero probability that a neutron or a y-ray may go through any thickness of any material without having an interaction. As a result, no finite range can be defined for neutrons or gammas. 

This method involves bombarding the sample with neutrons and measuring the radioactivity induced in the sample (commonly using gamma-ray spectrometry). In order to understand the principles of neutron activation analysis, some pertinent properties of neutrons and their interactions with matter will first be discussed. 

Detection of gamma or X rays by ionization or excitation is a secondary process where the first step is the formation of a free electron by interaction with matter. 

Ionizing radiation Particulate radiations (alpha, electron, neutron, proton) and electromagnetic radiations (X-rays and gamma rays) that have the ability to disrupt molecular bonds (ionize) when they interact with matter. 

There are a number of ways in which radiation can interact with matter, depending strongly upon the type of radiation. Since our primary interest is in neutron-produced reactions, we will discuss charged particle and gamma ray interactions only from the standpoint of shielding and detection. 

Interactions of Radiation with Matter 2.4.1 Gamma Ray Interactions... 

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