DEVICE FOR EVACUATING SINGLE CRYSTAL PULLING VESSEL

摘要

PROBLEM TO BE SOLVED: To reduce the electricity consumption by always operating a pump at indispensable minimum capacity. SOLUTION: The differential pressureΔP between the pressure Pc at the vessel 1 side and the pressure Pp at the pump 14 side with respect to a control valve 5 is detected by a differential pressure detecting means 6. Exhaust rate varying means 11 and 12 for varying the exhaust rate of the pump 14 are provided. Then, the exhaust rate varying means 11 and 12 are controlled by a control section 7 so as to make the exhaust rate of the pump 14 smaller according as the differential pressureΔP detected by the differential pressure detecting means 6 is larger.