AVS 49th International Symposium
    Vacuum Technology Thursday Sessions
       Session VT-ThM

Paper VT-ThM1
Cryopump Pumping Performance Estimation Using Flow Meter Method

Thursday, November 7, 2002, 8:20 am, Room C-104

Session: Gas Dynamics and Flow
Presenter: Y.-C. Lu, National Taipei University of Technology, Taiwan
Authors: H.-P. Cheng, National Taipei University of Technology, Taiwan
Y.-C. Lu, National Taipei University of Technology, Taiwan
M.-K. Hsu, World Hold Engineering Consultants, LTD
Correspondent: Click to Email
The pumping performance of cryopump, ULVAC CRYO-U10PU, is estimated by the flow meter method, which is widely used in the estimation of the pumping capacity of the turbo molecular pump for inlet pressure greater than 1.0E-04 Pa. The test dome is designed according to the instruction of JVIS-005 and connected directly with the cyropump. The inner diameter of the test dome is the same as the inlet port of the pump. The PIRANI gauge (ULVAC GP-1000, range 0.4 to 2700 Pa) and the ION gauge (ULVAC GI-1000 WIT, range 1.3E-05 to 6.7E-01 Pa) are equipped on the peripheral of the test dome to measure the test dome pressure according to the instruction of the JVIS-005. Four flow meters (Sierra 820 series, ranges 25 SCCM, 500 SCCM, 10 SLM, and 50 SLM) hybrid the needle valves are used to control the inlet gas throughput of the pump and two types of gas, nitrogen and argon are introduced. The variations of the temperature of the first stage (80K) of the cryopump and the test dome pressure relative to the operating time of cryopump are discussed. The pumping speed and throughput of the cryopump versus to the test dome pressure that is considered as the inlet pressure of cyropump are plotted and compared to the values described in the catalog of ULVAC. Finally, the residual gas analysis is made to investigate the residual gas in the whole system. And the temperature recovery time is recorded after the cryopump is turned off. According to the measurements, the temperature of the first stage of cryopump is in the steady state condition after two hundred minutes of the starting of the cryopump. The pumping speed for nitrogen is near to the value shown in the catalog of ULVAC and the argon is nearly twice than the catalog. The main residual gases are hydrogen and water at the status of the ultimate pressure operating condition. The recovery time from normal operating temperature of the cryopump to the room temperature is over three hundred minutes after the pump turned off.