Quantitative measurements of various gases in high and ultrahigh vacuum

Abstract

Two calibration methods for ionization gauges, a measurement method for the effective pumping speed of turbomolecular pumps, and a method for introducing low gas flow rates into vacuum chambers were examined. Twenty-four gases were used, including inert gases, hydrocarbons, oxygen, carbon oxide, chlorofluorocarbons, and liquid vapors. Direct comparison with a reference spinning rotor gauge and incorporation of the standard conductance element into the conductance modulation methods were tested as calibration methods in the range from 10−6 to 10−3 Pa. The effective pumping speed of a turbomolecular pump with a nominal pumping speed of 0.37 m3/s for N2 was measured using the modified conductance modulation method. A standard conductance element, which is a porous plug fabricated from sintered stainless steel, was tested in the range of 10−8 to 10−4 Pa m3/s to quantitatively introduce gas into a vacuum chamber. The obtained results were compared with previously reported values.