Enhancement of the intrinsic gamma-ray stopping efficiency of Geiger–Müller counters

Abstract

Geiger–Müller counters are frequently employed in many industrial radiation gauges. However, it is of practical interest to further extend the usage areas of these detectors to include applications such as dual modality densitometry and industrial gamma-ray tomography. This is mainly because these counters exhibit a high degree of robustness in demanding environments, their relatively low cost and the fact that they require simple read-out electronics. The main drawback of these counters is their relatively poor intrinsic gamma-ray stopping efficiency which is of the order of 1.0% for a wide range of primary photon energies. Therefore, identification of a method whereby the poor stopping efficiency in these detectors could be improved is of great interest. For this purpose Monte Carlo analyses were carried out, at photon emission energy of 59.5keV, to investigate the feasibility of introducing high density and high atomic number insulating disks inside a cylindrical Geiger–Müller counter. Calculations were performed using a specific purpose Monte Carlo code that was validated against experimental stopping efficiency data at 59.5keV. The preliminary simulation results show that a threefold increase in the efficiency of the counter could be expected as well as the fact that the simulation of secondary electron transport in the fill gas becomes critical. The results reported in this work also show that the maximum achievable low energy gamma-ray detection efficiency in Geiger–Müller counters is still significantly less than the efficiency of semiconductor and scintillation detectors at the corresponding photon energies. Therefore, the development of efficient Geiger–Müller counters will remain a challenge.