Absolute Sensitivity of a Thick-Walled Graphite Ionization Chamber For 1-GeV Photons

Abstract

A large number of different methods have now been developed for making absolute measurements on the flow of energy in the γ-ray beam emitted by electron accelerators with energies of 100 MeV and upward [1–4], These methods differ from one another in degree of accuracy, reliability, and convenience in operation. Recently R. Wilson’s apparatus [3], which has become known as a quantometer, has been the one most frequently used for making absolute measurements. The main advantage of this apparatus is the fact that its sensitivity depends very little on the energy of the photons [3,5], However, this advantage is accompanied by a number of failings: The construction and preparation are quite complicated, and the assembly has to be carried out very carefully indeed, as the gaps between the electrodes are very small. In fact, before using the quantometer one has to calibrate it very carefully by one of the more complicated but more reliable methods of absolute intensity measurement, for example, the calorimetric method or the pair spectrometer. For this reason it may prove troublesome to employ the quantometer in a number of specific cases.