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Title: Plasma chemistry in wire chambers

The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions ofmore » hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.« less
Authors:
Publication Date:
OSTI Identifier:
6813019
Report Number(s):
LBL-29033
ON: DE90013794; TRN: 90-023543
DOE Contract Number:
AC03-76SF00098
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis (M.S.)
Research Org:
Lawrence Berkeley Lab., CA (USA)
Sponsoring Org:
DOE/ER
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; PROPORTIONAL COUNTERS; WIRE SPARK CHAMBERS; AGING; ABLATION; CALIBRATION; GASES; PLASMA; POLYMERIZATION; SURFACE COATING; TEMPERATURE MEASUREMENT; CHEMICAL REACTIONS; DEPOSITION; FILMLESS SPARK CHAMBERS; FLUIDS; GAS TRACK DETECTORS; MEASURING INSTRUMENTS; RADIATION DETECTORS; SPARK CHAMBERS 440104* -- Radiation Instrumentation-- High Energy Physics Instrumentation