PRINCIPLES OF OPERATION OF THE DREO ATMOSPHERIC-SAMPLING PULSED NEGATIVE ION MASS SPECTROMETER

Authors
  1. Sewell, L.A.
  2. Pagotto, J.G.
Corporate Authors
Defence Research Establishment Ottawa, Ottawa ONT (CAN)
Abstract
The Chemical Protection Section at Defence Research Establishment Ottawa (DREO) recently acquired an atmospheric sampling pulsed negative ion mass spectrometer (PNIMS) from VG Instruments, U.K. This is the only commercially available instrument of this design. This unique instrument has a detection limit of one part per trillion (ppt) SF sub 6 in dry air and is able to detect SF sub 5- and SF sub 6- directly and selectively in humidified or dry air to an estimated detection limit of 150 ppt and 340 ppt respectively. This makes the DREO PNIMS the most sensitive instrument known that is capable of selective detection for this type of compound directly from humid air. The fast response time (much less than one second) and large, linear, dynamic range (six decades) enables this mass spectrometer to provide selective real time monitoring of SF sub 6 in air at sub-parts per billion (ppb) levels. Since this particular instrument is unique in the world, there are no manuals available which describe its operation. After reviewing the literature and conducting detailed discussions with the inventor, a series of sensitivity optimization experiments were performed. This technical note provides a detailed description of the basic principles behind the instrument's operation including an explanation of the unique source design, its ionization capabilities, and various recommended operating procedures.
Report Number
DREO-TN-92-18 — Technical Note
Date of publication
01 Oct 1992
Number of Pages
73
DSTKIM No
93-01118
CANDIS No
128285
Format(s):
Hardcopy;Originator's fiche received by DSIS

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