Anode wire aging tests with selected gases

As a continuation of earlier wire-aging investigations, additional candidates for wire chamber gas and wire have been tested. The gases include argon/ethane, HRS gas, dimethyl ether, carbon dioxide/ethane, and carbon tetrafluoride/isobutane. The wires used were gold-plated tungsten, Stablohm, Nicotin, and stainless steel. Measurements were made of the effects upon wire aging of impurities from plumbing materials or contamination from various types of oil. Attempts were made to induce wire aging by adding measured amounts of oxygen and halogen (methyl chloride), with negative results. The possible role of electronegativity in the wire-aging process is discussed, and measurements of electronegativity made with several single carbon Freons, using both an electron-capture detector and a wire chamber operating with dimethyl ether, are given. It is found that very pure dimethyl ether appears to be extraordinarily sensitive to materials in the gas stream, especially to certain plastics. However, with sufficient precautions, very good stability against aging was found with the resistive wires Stablohm and Nicotin