On the energy consumption of cryogenic systems and the choice of cryopumps

Energy consumption during the mutual use of cryogenic magnetic and vacuum systems including superconductina magnet, forevacuum and high vacuum cryopumps, is analyzed. The portion of energy consumption on preliminary condensational pumping-out of vaccuum chamber with volume of 6 m3 for the considered case does not exceed 12% and decreases in time. Summary portion of energy consumption on operation of forevacuum and high vacuum cryopumps does not exceed one third of energy consumption on preliminary cooling of superconducting magnet and decreases to 10% during stationary operation of cryogenic system during 85O hours. A comparison of general and specific energy consumptions during the operation of different condensational cryopumps as well as of forevacuum condensational and sorption pumps is made. A conclusion is made that at small periods of time (tens of hours) of cryovacuum system operation it is expidient to use one cryopump with a wide range of working pressures (atmosphere-superhigh vacuum) instead of a combination of forevacuum and high vacuum cryopumps. Besides, a conclusion is made on expediency of the use of nitrogen condensational pumps instead of nitrogen cryosorption ones in the range of high pressures (760-10 mm Hg) expecially during the pumping out of vacuum chambers of high volume (1m3 and higher). It is shown that account of energy consumptions on preliminary cooling of cryopumps and high vacuum ones in particular, at small (tens of hours) times of their operation increases average specific energy consumptions about 3 times. It is concluded that one can disregard the energy consumption used for preliminary cooling of cryopumps only in case of their stationary operation during about 103 hours