Analysis of compounds released from various detector materials and their impact on aging Characteristics of proportional counters

Outgassing properties of various detector materials have been studied. The thermal desorption tube method was used for sampling the compounds released from the materials. Analysis of the samples was carried out with a gas chromatograph/mass spectrometer analyzer. Attention was paid to compounds known to be easily polymerizing. Their impact on the aging characteristics of gaseous radiation detectors was studied by accelerated aging tests with the help of proportional counters. Styrene and some aromatic solvents were observed among the outgassing products of two different polyimide grades. In the accelerated aging tests both the styrene and the aromatic solvents were confirmed to cause a fast gain loss in the proportional counters filled with Ar/CH/sub 4/ gas mixture.