Is the effective accommodation coefficient of the spinning rotor gauge temperature dependent?

Abstract

The spinning rotor gauge (SRG) used as a vacuum gauge for the range of 10−4–1 Pa shows good long-term stability. Therefore it is widely used as a reference standard in calibration services. The calibration constant of the SRG is the effective accommodation coefficient σ with values around 1. This effective accommodation coefficient of the gas particles to the rotor is considered to be temperature independent for normal operational temperatures of 18–30 °C. We have carried out investigations that show that σ is slightly temperature dependent both for a baked and an unbaked rotor and vacuum system. The temperature range investigated was 16–40 °C. Relative changes of σ varied from 1×10−4 to 4×10−4/K. As the reason for the temperature dependence we could exclude neither a temperature dependent change of H2O coverage of the rotor nor a temperature dependence of the energy accommodation coefficient.