Cryogenics for the LEP200 superconducting cavities at CERN

The cryogenics for the LEP200 Project cover the cooling requirements of up to 64 modules containing each four superconducting (SC) cavities at 352 MHz RF. This includes both cooling for the cavities themselves by liquid helium boiling at 4.5 K, and use of cold helium gas for intercepting heat from accessories. Helium refrigeration is provided by separate powerful cryoplants at each of the four interaction points of LEP with 12 kW equivalent refrigeration at 4.5 K and cryogenic distribution lines of up to 810 m length, and by two 6 kW plants for the new test center SM18 where the acceptance tests of both SC cavities and magnets are carried out. Most of the hardware is installed, commissioning of the systems in LEP is progressing and experience in testing the new cavities from industry is accumulating. First conclusions and performance results are reported, and problems listed which require further work. >