Application of the Monte Carlo method to the calibration of detectors for gamma-ray astronomy

Abstract

The interpretation of the results of experiments in cosmic-ray and space physics is dependent on a good understanding of the performance of the instrumentation. Such a calibration may be obtained by use of an artificial stimulus, such as a beam of charged particles from an accelerator. The practical difficulties of such an approach, especially where the time scale is tied to the schedule of a satellite project, indicate the value of a theoretical estimation of the detector response. Since the particle interaction processes are of a statistical nature it is not usual to obtain analytical solutions to the problem. Instead a Monte Carlo technique is frequently employed in which the behaviour of individual particles is determined by randomly selected numbers and the response of the detector is derived by averaging over large samples of particles. The use of spark-chamber experiments in the field of gamma-ray astronomy has led to the development of Monte Carlo programmes to simulate the cascade processes in these experiments. Such a programme, developed in the Max Planck Institut für Extraterrestrische Physik, Garching-bei-München, has been recently extended for application to the study of the experiment which will form the payload of the ESRO satellite COS-B. Computations are being carried out in the European Space Research and Technology Centre and the results are presented in comparison with measurements made on a gamma-ray beam from the 500 MeV synchroton of Bonn University. The extension of the calculations to other experiment configurations and to energies beyond the range of the accelerator is discussed.