Cryogenics

Each of the Fermilab SCRF Test Facilities requires cryogenic support. Of these facilities, the single largest demand comes from the beam test facility at ILCTA-New Muon Lab (NML).

The cryogenic system at NML is planned to be a staged system. The first stage will utilize a Tevatron style satellite refrigerator and screw compressor to supply 4.5K liquification. A vacuum pumping skid, similar to the one used at the Meson Detector Building, will be used to lower the temperature to 2K. The warm thermal shield will be cooled with liquid nitrogen.

This system will be capable of cooling a single ILC cryomodule, however at a repetition rate below the ILC design of 5 Hz. The second stage will add a second satellite refrigerator, which will allow the operation of two ILC cryomodules at a repetition rate of 5 Hz.

Cryogenic Refrigerator Room at ILCTA-NML
Operation of an entire ILC RF unit (three cryomodules) with a repetition rate of 5 Hz will require a new cryogenic plant. This new plant will not only allow operation of an RF unit at design repetition rate, but will also operate the cryomodules with the ILC design low temperature and high temperature thermal shields. This will allow the thermal performance of the cryomodules to be properly assessed.

The NML cryogenics system is servicing an R&D facility that will need to have considerable flexibility for a wide range of loads including full operation at 5 Hz, and turn-down capability for operations with a few modules with static heat load only. It is assumed that the new helium plant would utilize turbo-expanders, oil-flooded screw compressors, and aluminum plate-fin heat exchangers. Pumping to 2 Kelvin may be by means of cold compressors, warm pumping, or a combination. Since this is expected to be staged installation, a pumping system utilizing warm pumping or combined cold and warm pumping will best match increasing cryogenic loads.

Overall plant efficiency is not a primary concern; emphasis instead is on flexibility, variable load capability, and reliability in supporting the needs of the test facility. The new cryogenic plant will allow us to operate a string of two RF Units at ILC temperature and pressure conditions.