Abstract
The Super-Conducting Fragment Separator (Super FRS) of the Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt is a large-acceptance superonducting fragment separator. The separator consists of large dipole, quadrupole and hexapole superconducting magnets. The long quadrupole magnet cryostat houses the helium chamber, which has the magnet iron and NbTi superconducting coil. The magnet weighs about 30 tons. The helium chamber is enclosed in vacuum inside the magnet cryostat. Multilayer Insulation (MLI) will be wrapped around the thermal shield to reduce radiation loss. Polyster of MLI comprises the major component responsible for outgassing. In order to reduce outgassing, pumping at elevated temperatures has to be carried out. In view of the large size and weight of the magnet, a seal off approach might not be operationally feasible. Continuous pumping of the cryostat has also been examined. Pump has been kept at a distance from the magnet considering the effect of stray magnetic fields. Oil free turbo molecular pump and scroll pump combination will be used to pump down the cryostat. The ultimate heat load of the cryostat will be highly dependent on the pressure attained. Radiation and conduction plays an important role in the heat transfer at low temperatures. This paper presents the vacuum design of the long quadrupole magnet cryostat and estimates the heat load of the cryostat.
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