Status, Operation and Performance of the RHIC Helium Refrigerator

The Relativistic Heavy Ion Collider RHIC helium refrigerator was modified from the refrigerator originally constructed fifteen years ago for the ISABELLE accelerator. The modifications include a new cold vacuum compressor and relocating the cold circulating compressor to the cryogenic distribution valve boxes, which are located near the cryogenic feed to the collider rings. Prior to start up, an extensive effort was spent on improving conditions of the compressor system, turbine skids, valves, instrumentation and control apChapautus. In February, 1996, the RHIC refrigerator was successfully cooled to liquid helium temperature with 10 kW of heat input at 4.5 K, 53 kW at 60 K and 44 g/s of liquefaction, using approximately two-thirds of the installed compressor capacity. In July, 1996, the refrigerator was used to cool a 350 meter vacuum jacketed transfer line and two cryogenic distribution valve boxes. In February, 1997, the refrigerator was used to cool the first RHIC sextant for over one month of operation. At the end of the first sextant test, an electric heat input of 25 kW at approximately 5.5 K was introduced to simulate a full refrigeration capacity mode. The capacity and reliability of the refrigerator have been demonstrated. The performance of the refrigerator including turbines, heat exchangers, cold vacuum compressor and circulating compressor is given.