Measurement of Low Outgassing-Rate in Self-Developed Pumping-Path Switching Algorithm:A Methodological Study

The low outgassing-rate of materials and devices in ultrahigh vacuum environment,including,but not limited to the stainless steel chamber-walls,microchannel-plate and ionization gauge,was precisely and repeatedly measured in the self-developed pumping-path switching(PPS) algorithm.The influence of the measurement techniques,including the pumping-path switching method,static pressure-rising method and orifice-conductance method,on the accuracy and uncertainty of the outgassing rate measurement was theoretically analyzed,numerically simulated with MOLFLOW software and experimentally evaluated.When it comes to outgassing rate evaluation,the simulated and measured results were found to be in good agreement.However,PPS algorithm outperforms the static pressure-rising and orifice-conductance methods not only because it is capable of measuring a much lower outgassing rate but also because it involves fewer error sources.