Development and demonstration of a supercritical helium-cooled cryogenic viscous compressor prototype for the iter vacuum system

As part of the vacuum system for the ITER fusion project, a cryogenic viscous compressor (CVC) is being developed to collect hydrogenic exhaust gases from the torus cryopumps and compress them to a high enough pressure by regeneration for pumping to the tritium reprocessing facility. Helium impurities that are a byproduct of the fusion reactions pass through the CVC and are pumped by conventional vacuum pumps and exhausted to the atmosphere. Before the development of a full-scale CVC, a representative, small-scale test prototype was designed, fabricated, and tested. With cooling provided by cold helium gas, hydrogen gas was introduced into the central column of the test prototype pump at flow rates between 0.001 g/s and 0.008 g/s. Based on the temperatures and flow rates of the cold helium gas, different percentages of hydrogen gas were frozen to the column surface wall as the hydrogen gas flow rate increased. Results from the measured temperatures and pressures will form a benchmark that will be used to judge future heat transfer enhancements to the prototype CVC and to develop a computational fluid dynamic model that will help develop design parameters for the full-scale CVC.