| 摘要 |
PURPOSE:To obtain an apparatus which does not generate danger such as explosion, etc. even in case a cryopump is stopped by always keeping the internal pressure of cryopump lower than a predetermined constant pressure. CONSTITUTION:When ion implantation is completed and a helium liquefier 17 is stopped by closing a valve 14 for vacuum exhaustion, temperature at the cryosurface 15 rises a gass pressure within the cryopump 4 also increases. A value of increased gas pressure is detected by a vacuum gauge 22 and then input to a control device 23 for cryo recovery. When a pressure value within the cryopump 4 reaches the upper limit vacuum degree P1, the signal for opening the rough- vacuum valve 19 is output to the rough-vacuum valve 19 from the control device 23. When the rough-vacuum valve 19 is opened, the interior of cryopump 4 is exhausted to the vacuum condition by an oil rotating pump 20. When a pressure value reaches the lower limit vacuum degree P2, the signal for closing the rough-vacuum valve 19 is sent to the rough-vacuum valve 19 from the control device 23.
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