Chemical model for wire chamber aging in CF[sub 4]/[ital i]C[sub 4]H[sub 10] gases

Journal Article · Sun Oct 31 23:00:00 EST 1993 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.354234· OSTI ID:5978760

Wise, J; Kadyk, J A ^[1]; Hess, D W ^[2]

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1. Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)
2. Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

Aging of proportional counters in CF[sub 4]/[ital i]C[sub 4]H[sub 10] mixtures is studied as a function of gas composition. Anode surfaces are analyzed by Auger electron spectroscopy. Anode-wire deposits are formed from 95/5 and 90/10 mixtures of CF[sub 4]/[ital i]C[sub 4]H[sub 10]; etching of deposits occurs in 50/50 and 80/20 mixtures of CF[sub 4]/[ital i]C[sub 4]H[sub 10] and in pure CF[sub 4]. Gold-plated wires are resistant to aging resulting from chemical attack by CF[sub 4], but non-gold-plated wires are too reactive for use in CF[sub 4]-containing gases. An apparent cathode aging process resulting in loss of gain rather than in a self-sustained discharge current is observed in CF[sub 4] and CF[sub 4]-rich gases. Principles of low-pressure rf plasma chemistry are used to interpret the plasma chemistry in avalanches ([ge]1 atm, dc). To understand anode aging in CF[sub 4]/[ital i]C[sub 4]H[sub 10] gases, a four-part model is developed considering: (i) plasma polymerization of [ital i]C[sub 4]H[sub 10]; (ii) etching of wire deposits by CF[sub 4]; (iii) deposition that occurs as a result of radical scavenging in strongly etching environments; and (iv) reactivity of the wire surface. Practical guidelines suggested by the model and application of the model to other fluorine-containing gases are discussed.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5978760
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 74:9; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360100 -- Metals & Alloys
440101* -- Radiation Instrumentation-- General Detectors or Monitors & Radiometric Instruments
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
AGING
ANODES
AUGER ELECTRON SPECTROSCOPY
CARBON COMPOUNDS
CARBON FLUORIDES
CHEMICAL REACTIONS
COATINGS
ELECTRODES
ELECTRON SPECTROSCOPY
ELEMENTS
ETCHING
FLUORIDES
FLUORINE COMPOUNDS
GOLD
HALIDES
HALOGEN COMPOUNDS
HYDROCARBONS
MEASURING INSTRUMENTS
METALS
MULTIWIRE PROPORTIONAL CHAMBERS
ORGANIC COMPOUNDS
PROPORTIONAL COUNTERS
RADIATION DETECTORS
SPECTROSCOPY
SURFACE FINISHING
TRANSITION ELEMENTS