Study of plasma chemistry in wire chambers by GC/MS

An apparatus to allow systematic and detailed study of radiation-induced plasma-chemical reactions that may lead to wire aging has been constructed. A proportional counter tube irradiated by a ⁵⁵Fe source is used as a model wire chamber. Less-volatile components in the tube effluent gas are concentrated by several orders of magnitude in a cryotrap to provide the sensitivity needed for detection. Separation and analysis are performed by gas chromatography/mass spectrometry (GC/MS). A study of the outgasses components from several different tubings has been made, and the observed products qualitatively identified. Two possible sources of silicon have been identified: incompletely cleaned parts that were once in contact with silicone oils or greases, and parts that may have had transient exposure to silicone vapors. A proportional tube has been used to model the plasma-chemical reactions that may occur in wire chambers, and a strong, reproducible signal has been observed