Geiger-Muller counter (GM-Counter)

Abstract

This article is about the Geiger-Muller counter which is the most versatile instrument for detecting the ionizing radiations.

If the electrodes of a gas filled counter are so shaped that there exists a high field near one of them even when a moderately high DC voltage is applied to it, then the amplification of an ionic charge reaches, in the region of high voltage, an avalanche condition. Practically, all of the gas present in the local volume of the electrode gets ionized. This results in a much larger voltage pulse on the electrode. The pulse height is independent of the amount of ionization originally produced by the particle. It depends only on the counter potential and increases with it. Only a single ion reaching the vicinity of the high voltage electrode may trigger the process. This counter is very simple to construct and is extremely sensitive to the passage of charged particles.