AVS 51st International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP17
Study of the Pump Pumping Performance after Heat is inputted into the Refrigerating Head of Cryopump

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: H.-P. Cheng, National Taipei University of Technology, Taiwan
Authors: H.-P. Cheng, National Taipei University of Technology, Taiwan
C.-W. Sun, National Taipei University of Technology, Taiwan
Y.-C. Lu, National Taipei University of Technology, Taiwan
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This study places the heater on the second refrigerating head of Cryopump of closed loop Gifford-McMahon (G-M) that uses helium for refrigerant, and applies different energy on the heater to investigate the pumping performance of Cryopump. The test system is constructed based on the test specification suggested by Welch, the Cryopump model is ULVAC-10PU. Pirani gauge and ion gauge are placed around the chamber to measure the chamber pressure. Before heat is transferred to the heater, the nitrogen and argon pumping speed of the pump is 919~2,170 liter/sec and 1,770~4,060 liter/sec, respectively. After heat is transferred to the heater, when the input watt increases, the temperature of cryopanel surface increases and pumping performance decreases. In the experiment of nitrogen gas, the heater is inputted with 2.5W, 5W, 7.5W, 10W, 12.5W, 15W, 17.5W, of which the decrease in pumping performance is the most apparent in 17.5 W; the pumping speed dropped to 230~625 liter/sec. The corresponding gas throughput is 0.2~63 SCCM. The tested chamber pressure is 1.6E-03~3.0E-01 Pa. In the experiment of argon gas, the heater is inputted with 2.5W, 5W, 7.5W, 10W, 12.5W, 15W, of which the decrease in pumping performance is the most apparent in 15 W; the pumping speed dropped to 507~1,350 liter/sec. The corresponding gas throughput is 0.28~63.45 SCCM. The tested chamber pressure is 1.0E-03~1.5E-01 Pa.