New Measurement Method of Outgassing Speed with a Sealed off Residual Gas Analyzer

The new measurement method of outgassing speed with a sealed off quadrupole residual gas analyzer (RGA) has been proposed. The unique feature of this method is that the high vacuum can be maintained by the self-pumping effect of the ultra low outgassing RGA. The newly-developed mass analyzer combined with BA-gauge is the key for this method. The pressure of chamber can be maintained below 2~5×10-7 Pa for a year without any pumping system. The majority of residual gases in the chamber were found to be hydrogen, methane and carbon-monoxide. In order to measure the outgassing speed of the RGA, the pumping speeds were measured by the self-pumping effect of RGA for hydrogen, deuterium, methane, nitrogen, carbon-monoxide, carbon-dioxide, oxygen and argon. When the pumping speed of RGA is balanced for outgassing from the RGA itself, we can calculate its value from the partial pressure in the spectrum. Then, we obtain the outgassing speeds for hydrogen=8.8×10-13 Pa m3/s, methane=1.2×10-13 Pa m3/s, carbon-monoxide=1.0×10-13 Pa m3/s.