Experience on 200K and liquid-He cryopumps installed in the large vacuum facilities at ESTEC/Noordwijk

The big vacuum chambers of the European Space Technology Centre, Noordwijk, for Space Simulation, vacuumtemperature cycling, for mechanical tests and for simulation of the pressure profile during the launch phase were equipped with 200K Cryopumps and partly additionally with liquid Helium cryopumps. The liquid He cryopumps proved to be very reliable, it is easy to adapt them for special tests and the cost for liquid Helium is considerable lower than often thought, actually it contributes only a few percent of the overall running cost of such a facility. The 200K-cryopumps are easier to operate, for longer tests (3 weeks), however, the pumps of higher capacity (>15 000 1/sec pumping speed) are unreliable, here some development is required. A smaller 200K cryopump (with CTI refrigerator) was running for 9000 hours without any failure and proved to be suitable as standard pump for continuous operation. (orig.)