Abstract
In order to examine the pumping performance of the scroll pump for various gases, the following two experiments were performed : (1) Measurement of the ultimate pressure for Argon, Nitrogen and Helium; (2) Separation of the direct effect of orbiting speed on the ultimate pressure from the effect of clearance change with temperature change accompanying a variation in orbiting speed. For these experiments, the apparatus was improved as follows : (1) The pump was strengthened with double seals to prevent leakage from the atmosphere; (2) A dry ice trap was put between the vacuum chamber and the vacuum gauge for the purpose of removing the water vapor; (3) A tank connected to the discharge mouth is filled with test gas, whose pressure is a little higher than the atmosphere, in order to avoid other-gas contamination. The results were compared with the theoretical predictions, and the validity of the theory was confirmed to a certain extent.
