Outgassing Measurement for Vacuum Engineering

In this article, two common methods to evaluate the outgassing properties of vacuum system materials, thermal desorption spectroscopy (TDS) and the method of switching between two pumping paths (SPP), are discussed. TDS can evaluate the outgassing properties of small samples, while SPP method can measure low outgassing rate, such as the case after baking. Ion gauges and/or quadrupole mass spectrometers (QMS) consist of the TDS and SPP setups. In these cases, QMS are typically calibrated using a standard conductance element (SCE). The calibration using the SCE enables the direct conversion of the QMS ion current into the gas flow rate.