A Study of the Deterioration of Methane-Filled Geiger-Müller Counters

The changes in the characteristics of methane-filled Geiger-Müller counters were studied as a function of counter life. It was found that the counters had a useful life of between ${10}^7$ and ${10}^8$ counts. Mass-spectroscopic analysis of the gas during the life of the counter showed the major decomposition products in the gaseous phase to be hydrogen, ethane, ethylene, and acetylene. These changes in gas composition did not account for the counter deterioration. The heavy hydrocarbon products deposited on the electrodes resulted in counter failure.