Inner pressure measurement of turbo molecular pump

The pressure of the gas including free molecular, transition, slip, and con tinuum flow inside the turbo booster pump is successfully measured in this study. This pump was developed through the cooperation of Kashiyama Industr ies Ltd. and Precision Instrument Development Center, with the goal of repl acing the mechanical booster pump. The flow-meter method of Japan's standar d JVIS-005 is adopted here to simulate the operating condition of the pump in different pressure ranges. The laboratory and the experimental apparatus are constructed according to the International Standards Organization and JVIS standards. In order to measure the pressure variations from the pump i nlet to the outlet, nine holes with 6.5 mm inner diameter are drilled throu gh the pump casing around the periphery along the axial direction. The dist ances of these holes from the plane of the inlet port are 49.5, 79.5, 107, 127, 147, 167, 187, 207, and 227 mm. The metal gasket face seal fittings wi th inner diameter 3 mm are welded into the holes using the TIG-tungsten ine rt gas welding method. The metal bellow tube is used to link the vacuum gau ges and the metal gasket face seal fittings. The accuracy range of the vacu um gauges is 1.33X10(-4)-133 mbar. Six cases of the pump inner pressure wit h the pump inlet pressure 1.33X10(-4), 1.33X10(-3), 1.33X10(-2), 0.133, 0.6 65, and 1.33 mbar are performed. The pressure variations along the axial di rection are plotted. The pressure trend related to the rotor shape is discu ssed. The pressure discrepancies between the measured and calculated done b y the Computational fluid dynamics method are compared. (C) 2000 American V acuum Society. [S0734-2101(00)01903-7].