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Title: Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer

Abstract

One must do ultrasensitive leak detection during ultrahigh-vacuum (UHV) evacuation, especially just before the device is sealed off from the vacuum system, to guarantee the longevity of the sealed high-vacuum or even UHV devices with small volume. A quadrupole mass spectrometer (QMS) with an UHV evacuation system can be used under accumulation mode to do the testing. Possible accumulate modes, as well as their advantages and shortcomings, are studied experimentally and discussed in this paper. We found that the opening action of the metal valve during accumulation mode always severely affects the height of the peak indicated by QMS and causes considerable errors. If we determine the leak rate by the peak area instead of the peak height, the situation is much improved. This method has proven quite useful in ensuring the tightness quality for complex sealed UHV devices with small volumes. Ultrasensitive leak detection has been carried out for such real evacuating devices, and a leak rate of 2x10{sup -14} Pa{center_dot}m{sup 3}/s was detected, which is far lower than its dynamic mode and the detection limit of the current advanced commercial leak detectors.

Authors:
; ; ; ;  [1]
  1. Department of Electronic Engineering, Tsinghua University, Beijing, 100084 (China)
Publication Date:
OSTI Identifier:
20776952
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films; Journal Volume: 24; Journal Issue: 1; Other Information: DOI: 10.1116/1.2137330; (c) 2006 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; DETECTION; LEAK DETECTORS; LEAKS; MASS SPECTROMETERS; OPENINGS; PEAKS; TESTING; VACUUM SYSTEMS; VALVES

Citation Formats

Chen Xu, Huang Tianbin, Wang Ligong, Jin Qiji, and Cha Liangzhen. Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer. United States: N. p., 2006. Web. doi:10.1116/1.2137330.
Chen Xu, Huang Tianbin, Wang Ligong, Jin Qiji, & Cha Liangzhen. Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer. United States. doi:10.1116/1.2137330.
Chen Xu, Huang Tianbin, Wang Ligong, Jin Qiji, and Cha Liangzhen. Sun . "Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer". United States. doi:10.1116/1.2137330.
@article{osti_20776952,
title = {Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer},
author = {Chen Xu and Huang Tianbin and Wang Ligong and Jin Qiji and Cha Liangzhen},
abstractNote = {One must do ultrasensitive leak detection during ultrahigh-vacuum (UHV) evacuation, especially just before the device is sealed off from the vacuum system, to guarantee the longevity of the sealed high-vacuum or even UHV devices with small volume. A quadrupole mass spectrometer (QMS) with an UHV evacuation system can be used under accumulation mode to do the testing. Possible accumulate modes, as well as their advantages and shortcomings, are studied experimentally and discussed in this paper. We found that the opening action of the metal valve during accumulation mode always severely affects the height of the peak indicated by QMS and causes considerable errors. If we determine the leak rate by the peak area instead of the peak height, the situation is much improved. This method has proven quite useful in ensuring the tightness quality for complex sealed UHV devices with small volumes. Ultrasensitive leak detection has been carried out for such real evacuating devices, and a leak rate of 2x10{sup -14} Pa{center_dot}m{sup 3}/s was detected, which is far lower than its dynamic mode and the detection limit of the current advanced commercial leak detectors.},
doi = {10.1116/1.2137330},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 1,
volume = 24,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • The characteristics of a small quadrupole mass spectrometer are described in detail. These show that the requirements of an analytical instrument for use in high and ultrahigh vacuum systems have been met. The performance is adequate for the measurement of partial pressures down to and below 10/sup -11/ torr. This is achieved with constant sensiiivity over the range 0 to 200 amu with a resolution adequate to separate completely individual peaks up to 50 amu. The instrument does not have an electron multiplier. The consequent disadvantages of a relatively slow response and a limitation to the minimum detectable pressure aremore » compensated by a higher stability and a smaller, simpler, and reliable instrument. Observations with a number of units over a period of many months indicate a maximum change in sensitivity of any one and a difference between individual instruments to be of the order of plus or minus 20%. This is therefore a gauge head of approximately the same size as a modulated BA gauge with the same sensitivity, stability, and baking characteristics. (auth)« less
  • Air mass spectrometer leak detection is being utilized in the Gas Centrifuge Enrichment Plant as a method of rapidly localizing leaks in this extremely large and complicated maze of process piping. A SALT cart has been developed to minimize the time and problems such as long time constants, helium permeation, low pumping speeds, and large helium hoods associated with helium mass spectrometer leak detection. By using the SALT cart to positively indicate the presence of air, in conjunction with process valve manipulations, leaks can be quickly localized to specific sections of piping. This process saves time and effort which wouldmore » otherwise be spent helium probing nonleaky sections. Once a leak has been localized, the SALT cart can aid in pinpointing the leak using various tracer gases. A helium mass spectrometer leak detector may also be placed in series with the SALT cart taking full advantage of the SALT's high speed and the leak detector's high sensitivity. Cart design will be discussed in addition to testing methods and sample results.« less