Gamma Rays: Applications in Environmental Gamma Dosimetry and Determination Samples Gamma-Activities Induced by Neutrons

Abstract

Gamma rays are high frequency electromagnetic radiation and therefore carry a lot of energy. They pass through most types of materials. Only an absorber such as a lead block or a thick concrete block can stop their transmission. In many alpha and beta transitions, the residual nucleus is formed in an excited state. The nucleus can lose its excitation energy and move to a “ fundamental level ” in several ways. (a) The most common transition is the emission of electromagnetic radiation, called gamma radiation. Very often the de-excitation occurs not directly between the highest level of the nucleus and its basic level, but by “ cascades ” corresponding to intermediate energies. (b) The gamma emission can be accompanied or replaced by the electron emission so-called “ internal conversion ” , where the energy excess is transmitted to an electron in the K, L or M shell. (c) Finally, if the available energy is greater than 2m e c 2 = 1022 keV, the excited nucleus can create a pair (e + , e (cid:1) ). The excess energy appears as a kinetic form. This internal materialization process is very rare. In this chapter we are presenting two applications of gamma rays: On the one hand, TL dosimeters and field gamma dosimetry are studied, a careful study of the correcting factors linked to the environmental and experimental conditions is performed. On the other hand, we are presenting a calculation method for controlling neutron activation analysis (NAA) experiments. This method consists of simulating the process of interaction of gamma rays induced by irradiation of various samples.