Shower-Type Gamma Spectrometers, Theory and Calculation of the Principal Characteristics

Abstract

The majority of experimental methods of determining the energy of y quanta are based on the measurement of the energy distribution of secondary particles created in matter by the y radiation. Prominent among these are methods based on using a “thick” radiator and measuring the energy of the particles arising in this [1]. An important feature of the γ spectrometer with a thick radiator is the high recording efficiency. As regards resolving power, however, these spectrometers are inferior to those with thin radiators, because of the multitude of processes taking place in the actual radiator and the consequent spread in the evolution of energy. In order to reduce the intrinsic width of the γ-spectrometer line in the low-energy range, we may either limit the number of processes constituting the main contribution to the formation of the line, or else ensure conditions such that none of the secondary particles should leave the radiator, i. e., conditions ensuring complete absorption. As the energy of the γ quanta recorded increases, the character of the processes taking place in the radiator becomes much more complex, so that complete absorption is in fact the only method of ensuring a minimum intrinsic line breadth for a thick-radiator y spectrometer.