High Sensitivity Mass Spectrometer Leak Detector

1960 ◽  
Vol 31 (7) ◽  
pp. 720-723 ◽  
Author(s):  
N. R. Daly
Author(s):  
Y. Tito Saski

Gas leakage between E-11 and E-15 std cc He/s can be measured by a helium accumulation method. The leak detector uses a quadrupole mass spectrometer with a minimum detectable partial pressure of 5E-15 torr. The mass spectrometer is attached to a small ultrahigh vacuum chamber constructed of stainless steel treated for a low hydrogen outgas rate of 2E-15 torr·liter/cm2·s. The chamber has a nozzle to which a test object can be attached. The chamber is also equipped with a non-evaporable getter (NEG) pump that pumps active gases but not noble gases such as helium. The purpose of the NEG and the ultra-low hydrogen outgas feature of the chamber is to maintain low background pressure and high sensitivity of the quadrupole during helium accumulation. Helium tracer gas coming through a defective seal or material is accumulated in this chamber for a few minutes, and the rate of rise of the helium signal is compared with that of a calibrated reference leak. In this manner, leakage down to 1E-15 std cc He/s can be measured with a good confidence factor.


1975 ◽  
Vol 58 (4) ◽  
pp. 734-742 ◽  
Author(s):  
Richard Saferstein ◽  
Jew-Ming Chao ◽  
John J Manura

Abstract The detection of explosive residues in debris is difficult because of the thermal instability of many explosives along with the high sensitivity requirements of the analyses. The isobutane chemical ionization (CI) mass spectra of common civilian and military explosives were obtained under different instrumental parameters. The intent of the study was to determine the feasibility of applying CI to residue detection. The CI spectra of the explosives 1,3,5-trinitro-1,3,5-triazocydohexane, 1,3,5,7-tetraazocyclooctane, and pentaerythritol tetranitrate were shown to be particularly sensitive to the conditions of source temperature and reagent gas pressure. These parameters were adjusted to yield the least complex CI spectra for the explosives studied. The simplicity of the CI spectra obtained makes it a feasible technique for detecting explosive residues in the presence of extraneous materials found in the acetone extracts of debris material. Placement of the extract into the direct probe of the CI mass spectrometer eliminates the need for prior chromatographic treatment of the extract and would optimize the high sensitivity of the CI technique.


2014 ◽  
Vol 568-570 ◽  
pp. 395-400
Author(s):  
Kai Ni ◽  
Xiang Yan ◽  
Quan Yu ◽  
Zu Hua Shi ◽  
Xin Qiong Lu ◽  
...  

Air core transformer is an essential part of mass spectrometer. Test coil is often used to measure its resonant frequency with the advantages of easy installation and high sensitivity. However, the influence of test coil while it is installed close to the working coils on the transformer is not studied before. To reveal the influence of test coil and determine the right position to install, two experiments using test coil and opened probe respectively for the measurement are conducted. Since the opened probe has little load effect on the original transformer impedance system, it can be used to validate the influence of test coil. By comparing the two experimental results, we find that the right position to install the test coil is on the further side of the primary coil to the secondary coil. This work allows us to integrate the test coil with the air core transformer to monitor the resonant frequency in real-time.


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