AVS 52nd International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM6
The Effect of Heat Radiation on the Pumping Performance of Cryopump

Wednesday, November 2, 2005, 10:00 am, Room 201

Session: Gas Flow and Pump Technology
Presenter: H.-P. Cheng, National Taipei University of Technology, R.O.C.
Authors: H.-P. Cheng, National Taipei University of Technology, R.O.C.
Y.-H. Shen, National Taipei University of Technology, R.O.C.
C.-W. Sun, National Taipei University of Technology, R.O.C.
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In this study, the quartz lamp was placed at the center top of the vacuum chamber of the G-M Cryopump. Measurements of the throughput, pumping speed, and the temperature of the cryopanel surface inside the Cryopump based on different energy levels of the quartz lamp were taken, in order to discuss the effect of quartz lamp energy on the pumping performance after transmitted to the inside of the Cryopump by means of heat radiation. The test system was built based on the standard suggested by Welch, the tested Cryopump was ULVAC-10PU. Before the transmission of heat by the quartz lamp, the measured pumping speed for nitrogen was 1,573~2,423 Liter/sec when the chamber pressure was controlled at 2.0E-03~1.3E-01Pa, and the throughput were 1.71~171.52 SCCM. The first-stage cryopanel surface temperatures were 66.52~85.27K, second-stage cryopanel surface temperatures were 9.93~12.73K. After transmitting heat energy of 5, 10, 15, 20W by the quartz lamp, the pumping performance of the Cryopump deteriorated, the temperatures of first- and second- stage cryopanel surfaces increased, while the increase of first-stage cryopanel surface temperature was more significant. When nitrogen was used as the testing gas, the increase of temperature inside the Cryopump was most significant when the energy of the quartz lamp was 20W. When the chamber pressure was 2.0E-03~1.3E-01 Pa, the throughput in the chamber was 1.61~145.65 SCCM, the pumping speed dropped to 1,476~2,058 Liter/sec, the temperatures of first- and second- stage cryopanel surfaces increased from 103.03K and 12.03K to 126.03K and 14.9K, respectively. Based on the above data, when the heat radiation of quartz lamp was 20W, the temperatures of first- and second- stage cryopanel surfaces were reaching the upper limit of the standard suggested by Welch, thus, it is not recommended to increase the quartz lamp energy.