Consequences of plasma disruption mitigation by massive gas injection on the ITER torus cryopumping system

The ITER torus exhaust pumping system is based on six primary vacuum cryogenic pumps, and a rough and regeneration pumping system that can pump the exhaust gases from the torus cryopumps to the tritium plant. Massive gas injection is a proposed concept to mitigate plasma disruptions in ITER. The present paper identifies the limitations and down-times of the ITER torus pumping system after a massive gas injection event. Deuterium, helium, neon, and argon injections are discussed. The resulting high pressure in the torus is leading to high mass flows and heat fluxes to the cryogenic pumps, resulting in a significant and rapid temperature increase of the pumping surfaces normally cooled at 5 K. However, the consequences on the torus pumping system operation depend on the gas species and quantities injected. Finally, the regeneration of the cryopumps, the rough pumping of the torus, and the overall torus pumping system turnover time until vacuum and thermal conditions for the start of the next plasma pulse are initiated again are discussed.