Optimization of the operation of the small quadrupole mass spectrometer to give minimum long-term instability

Abstract

Changes in sensitivity and resolution of a small quadrupole residual gas analyser operating in a relatively hostile environment have been studied over a period of one year. The changes in sensitivity, almost invariably a drift to lower values, have been shown to be dependent upon contamination at the entrance to the filter. It was found that this deterioration of performance could be reduced to a minimum by injecting ions into the filter with a relatively high energy. This is a factor which should be taken into account when the operating parameters of any instrument are being determined, particularly when measurements are to be made in a system where frequent re-calibration is not practicable.