OPTIMIZATION OF THE OPERATION OF THE SMALL QUADRUPOLE MASS-SPECTROMETER TO GIVE MINIMUM LONG-TERM INSTABILITY

Changes in sensitivity and resolution of a small quadruple residual gas analyser operating in a relatively hostile environment 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.