Remarks concerning about the characteristics of the extractor vacuum gauge and the Quadrupole Mass Spectrometer

Abstract

In this study, the stability of an extractor gauge (EXG) was investigated through the determination of correction factors (CFs) over a pressure range 5 × 10−5 Pa to 9 × 10−3 Pa by using a Spinning Rotor Gauge (SRG) traceable to UME Static Expansion System, during 20 months and 15 months for N2 and He, respectively. Percent and fractional changes in CFs were studied and sensitivities of EXG were also presented for Ar and CO2. Direct comparison method was used for EXG stability measurements. Additionally, sensitivity measurements of Quadrupole Mass Spectrometer (QMS) were performed in the range of 1.0 × 10−6 Pa to 1.0 × 10−2 Pa at emission currents of 2 mA, 0.4 mA and 0.1 mA for He, N2 and Ar. Long-term stabilities of QMS for N2 and He were analyzed for about 2 years. EXG and SRG were used for QMS sensitivity measurements.The changes in CF of EXG remained within ±5% and ±6%, and fractional changes remained within about ±0.03 and ±0.05 for seven and five different measurement runs for N2 and He, respectively. The change in CF of EXG based on the mean value of the relevant pressure point is 5.8% and 7.8% at 5 × 10−5 Pa, 5.3% and 5.9% at 9 × 10−3 Pa, and maximum CF changes relative to the first calibrations ranges from −1.7% to 2.4% and from −1.0% to 4.7% within the selected pressure range for N2 and He, respectively. The changes of QMS sensitivity are strongly dependent to the electron current. Maximum changes of QMS sensitivities over a three month period are 44% and −35% for N2 and He, respectively. This study was conducted in the frame of EMRP IND12 “Vacuum Metrology for Production Environments” project that was funded by the European Metrology Research Programme (EMRP).