PURPOSE: To enable exhaustion from low vacuum region to high vacuum region, by coupling two types of sump pums for exhausting different gas and a pass- through pump to a vacuum tank while coupling a vacuum pump to said pass- through pump.

CONSTITUTION: A cryo-pump 2 and a suction pump 3 as a sump pump are coupled to a vacuum tank 1 while a pass-through pump 4 and a vacuum pump 5 are coupled sequentially to said pass-through pump 4. The cryo-pump 2 will condence and collect gas except H2, Ne and He having steam pressure lower than 10-12Torr on the cooling face. The suction pump 3 will suck/exhaust He and Ne having steam pressure higher than 10-12Torr even under cryo-temperature of 10W20°K while the pass-through pump 4 will selectively pass He which has not exhausted through cryo-pump 2 and suction pump 3 and discharge through the vacuum pump 5. Consequently, all gas can be exhausted under wide pressure range.