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Title: Simple catalytic cell for restoring He leak detector sensitivity on vacuum systems with high D{sub 2} backgrounds

Abstract

The DIII{endash}D National Fusion Facility at General Atomics (GA) focuses on plasma physics and fusion energy science. The DIII{endash}D tokamak is a 35 m{sup 3} toroidal vacuum vessel with over 200 ports for diagnostic instrumentation, cryogenics, microwave heating, and four large neutral beam injectors. Maintaining vacuum in the 10{sup {minus}8}&hthinsp;Torr range is crucial for producing high performance plasma discharges. He leak checking the DIII{endash}D tokamak and the neutral beamlines has historically been difficult. D{sub 2} is used as the fuel gas in most plasma discharges and neutral beams. After plasma operations, D{sub 2} outgassing from the torus walls and internal beamline components can exceed 10{sup {minus}4}&hthinsp;std&hthinsp;cm{sup 3}/s. The mass of the D{sub 2} molecule (4.028 u) is indistinguishable from that of the He atom (4.003 u) to a standard mass spectrometer leak detector. High levels of D{sub 2} reduce leak detector sensitivity and effectively mask the He trace gas signal rendering normal leak checking techniques ineffective. A simple apparatus was developed at GA to address these problems. It consists of a palladium based catalyst cell and associated valves and piping placed in series with the leak detector. This reduces the D{sub 2} throughput by a factor greater than 10&hthinsp;000, restoringmore » leak detector sensitivity. This article will briefly discuss the development of the cell, the physical processes involved, the tests performed to quantify and optimize the processes, and the operational results at DIII{endash}D. {copyright} {ital 1999 American Vacuum Society.}« less

Authors:
;  [1]
  1. General Atomics, San Diego, California 92186-5608 (United States)
Publication Date:
OSTI Identifier:
359800
Report Number(s):
CONF-981126-
Journal ID: JVTAD6; ISSN 0734-2101; TRN: 9914M0048
Resource Type:
Journal Article
Journal Name:
Journal of Vacuum Science and Technology, A
Additional Journal Information:
Journal Volume: 17; Journal Issue: 4; Conference: 45. annual American Vacuum Society symposium and topical conference, Baltimore, MD (United States), 2-6 Nov 1998; Other Information: PBD: Jul 1999
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; TOKAMAK DEVICES; HELIUM; LEAK DETECTORS; CATALYSIS; DEUTERIUM; PALLADIUM; VACUUM SYSTEMS; FUEL FABRICATION PLANTS

Citation Formats

Busath, J., and Chiu, H.K. Simple catalytic cell for restoring He leak detector sensitivity on vacuum systems with high D{sub 2} backgrounds. United States: N. p., 1999. Web. doi:10.1116/1.581720.
Busath, J., & Chiu, H.K. Simple catalytic cell for restoring He leak detector sensitivity on vacuum systems with high D{sub 2} backgrounds. United States. doi:10.1116/1.581720.
Busath, J., and Chiu, H.K. Thu . "Simple catalytic cell for restoring He leak detector sensitivity on vacuum systems with high D{sub 2} backgrounds". United States. doi:10.1116/1.581720.
@article{osti_359800,
title = {Simple catalytic cell for restoring He leak detector sensitivity on vacuum systems with high D{sub 2} backgrounds},
author = {Busath, J. and Chiu, H.K.},
abstractNote = {The DIII{endash}D National Fusion Facility at General Atomics (GA) focuses on plasma physics and fusion energy science. The DIII{endash}D tokamak is a 35 m{sup 3} toroidal vacuum vessel with over 200 ports for diagnostic instrumentation, cryogenics, microwave heating, and four large neutral beam injectors. Maintaining vacuum in the 10{sup {minus}8}&hthinsp;Torr range is crucial for producing high performance plasma discharges. He leak checking the DIII{endash}D tokamak and the neutral beamlines has historically been difficult. D{sub 2} is used as the fuel gas in most plasma discharges and neutral beams. After plasma operations, D{sub 2} outgassing from the torus walls and internal beamline components can exceed 10{sup {minus}4}&hthinsp;std&hthinsp;cm{sup 3}/s. The mass of the D{sub 2} molecule (4.028 u) is indistinguishable from that of the He atom (4.003 u) to a standard mass spectrometer leak detector. High levels of D{sub 2} reduce leak detector sensitivity and effectively mask the He trace gas signal rendering normal leak checking techniques ineffective. A simple apparatus was developed at GA to address these problems. It consists of a palladium based catalyst cell and associated valves and piping placed in series with the leak detector. This reduces the D{sub 2} throughput by a factor greater than 10&hthinsp;000, restoring leak detector sensitivity. This article will briefly discuss the development of the cell, the physical processes involved, the tests performed to quantify and optimize the processes, and the operational results at DIII{endash}D. {copyright} {ital 1999 American Vacuum Society.}},
doi = {10.1116/1.581720},
journal = {Journal of Vacuum Science and Technology, A},
number = 4,
volume = 17,
place = {United States},
year = {1999},
month = {7}
}