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The cryogenic systems at Jefferson Laboratory (JLAB) consist of four 4 Kelvin and two 2 Kelvin helium refrigerators in three plant locations.  The main machine is in the accelerator site and is located at the Central Helium Liquefier (CHL) facility.  The CHL also houses the Standby Refrigerator (SBR).  The End Station Refrigerator (ESR) is also in the accelerator site.  The Cryogenic Test Facility (CTF) is located on the main JLAB campus behind the Test Lab.  These plants are used to support the laboratory's Continuous Electron Beam Accelerator, Free Electron Laser Facility, Cryomodule Test Facility, and the superconducting magnets/targets of three Experimental Halls.  These plants represent plants built as early as 1977 and appear much the same as they did during their construction but have been modified for the JLAB applications and are very different from a technology point of view.

In the past, large scale helium cryogenic systems in the United States saw dramatic steps in both scale and technology with each passing commercial and experimental laboratory application.  As the end user applications grew, so did the challenges of engineering cryogenic systems never attempted before.  Many new technologies had to be developed to support the application.  An early 1970's 300 watt refrigerator would have been a very large machine.  Then within a short time (mid-late 1970's) came the LANL M4000 (now at SLAC), 4K 1500 watt LBL Escar/FERMI refrigerators and the 3.5K ORNL plant.  The large FERMI Big "L" 5KW 4K liquefiers of the 1980's moved the refrigerator "performance bar" up once again, becoming the world's largest.  This was followed by the very large BNL Isabelle 3.5K refrigerator and the JLAB 2K 4.6KW refrigerator.  For the JLAB 2K refrigerator the technology change from a previous 5 g/s plant (Torre-Supra) to 235 g/s using centrifugal cold compressors equipped with cryogenic technology had to be nurtured and developed in advance.  JLAB cryogenic senior staff engineers were fortunate to be part of the design of all of the plants listed above in their earlier industrial cryogenic careers and have seen the introduction of components such as oil flooded screw compressors, silicon diode temperature sensors turbine expanders cold compressors, effective oil removal, contamination control, and the change from pneumatic to computer controls.

Since 1988 through the present day the JLAB plants have under gone an evolution of further design change and technology enhancements.  Building on the experiences of the past, these changes focus on system performance, efficiency and high reliability with an eye to future technology requirements.  For JLAB this has included the development of the "Ganni Helium Process Cycle" and "Improved Multi pass LN2 Helium Pre-cooling", as well as automated plant capacity control which varies the amount of utility used while matching the refrigeration produced to a varying load.  All of which was developed to meet the user needs of economy and performance.

As JLAB plans to upgrade its current accelerator from 6 GEV beam operations to 12 GEV beam operations, the need to double the current JLAB 2K refrigeration CHL plant capacity will follow all of the past history of cryogenic helium plant design and operation...better technology with economy and reliability.