Anode Wire Aging Measurements and a Search for Remedies

As part of a continuing investigation into the aspects of the aging process induced by radiation, measurements have been made of anode wire gain loss in a typical gain region. This has been done for several gas mixtures, but with emphasis on measurements of 50% argon + 50% ethane. Parameters such as gain, gas flow rate and small concentrations of certain additives were investigated to determine their effects on the gain loss rate. The effects of ethanol, water, and isopropanol vapor at about 1% concentration were studied, as well as potential contributions to aging from different types of plastic tubing in the gas system. The results were found to be quite sensitive in certain cases to the wire surface material, to additives such as the alcohols tested, and to small gas impurities. Certain pure gas mixtures were found to be consistent with no aging at the sensitivity level of this technique.