Performance Assessment of 35 Cold Hydrodynamic Compressors for the 1.8 K Refrigeration Units of the LHC

The cooling capacity below 2 K for the superconducting magnets in the Large Hadron Collider (LHC), at CERN, will be provided by eight refrigeration units of 2400 W at 1.8 K, each of them coupled to one 18 kW at 4.5 K refrigerator. The supply of the series units was linked to successful testing and acceptance of the pre-series units delivered by the two selected vendors. The two pre-series units were temporarily installed in a dedicated test station to validate the overall capacity and to properly assess the performance of specific components such as cold compressors. Then the cold compressor cartridges to be installed in the six series and associated spare cartridges have been intensively and systematically tested in the test station. After a brief description of the test bench and the main achieved features of the pre-series units, we will present the results of the tests of 35 cold compressor cartridges. These tests show isentropic efficiency in the 75% range, excellent reproducibility and interchange ability. Some process and system specificities observed will be reported and finally perspectives will be proposed.