Open AccessCalibration of pressure‐dependent sensitivity and discrimination in Nier‐type noble gas ion sources
Author(s) -
Burnard P. G.,
Farley K. A.
Publication year - 2000
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2000gc000038
Subject(s) - spectrometer , noble gas , mass spectrometry , sensitivity (control systems) , voltage , calibration , ionization , analytical chemistry (journal) , total pressure , ion , optics , atomic physics , materials science , chemistry , physics , mechanics , organic chemistry , chromatography , quantum mechanics , electronic engineering , engineering
The efficiency of many noble gas mass spectrometers to ionize gas species is known to be a function of the pressure of gas in the spectrometer. This work shows how the half plate voltage for maximum He or Ar signal depends on the spectrometer pressure and shows that the half plate voltage for maximum 4 He sensitivity does not coincide with the half plate voltage for maximum 3 He sensitivity. In addition, half plate voltage has a greater control on sensitivity at higher spectrometer pressures. Variations in He and Ar sensitivity and isotopic discrimination as a function of pressure are due, at least in part, to these variations in the position of maximum sensitivity with respect to half plate voltage. The maximum sensitivity settings shift to lower half plate voltage at high spectrometer pressures, irrespective of if the pressure increase is due to the gas being investigated or a different species. Therefore noble gas mass spectrometers should always be tuned at the maximum possible pressure; measurements at higher pressures should be avoided. Significant errors in the spectrometer sensitivity and discrimination can result from improper tuning and calibration of noble gas mass spectrometers.