Supercritical helium as a coolant for DIII–D cryopumps

The DIII–D tokamak uses three cryocondensation pumps for plasma density control. Each DIII–D pump consists of a series of concentric stainless steel tubes assembled together. The two phase (TP) helium was chosen for DIII–D because it is available at the DIII–D site and is used for neutral beam (NB) and other applications. The three pumps inside DIII–D have performed as expected for the last several years. onducting machines under construction, such as KSTAR and SST-1 have supercritical (SC) helium available on site. The device operator would prefer to use it for cooling the cryocondensation pumps. sign of the DIII–D cryocondensation pump is simple, robust, inexpensive and reliable. This study was undertaken to evaluate if the supercritical helium can be used as a coolant for the GA design of the cryocondensation pump.