The Commissioning of the WEST Tokamak: Experience and Lessons Learned

The integrated commissioning of the tungsten (W) environment in steady-state tokamak (WEST) was started with the superconducting magnet cool-down and completed one year after by the injection of 2.5 MW of additional power. It consisted of several steps: local system commissioning, integrated commissioning without plasma, and first plasma operation. This article reviews these WEST commissioning phases and highlights the experiences and the lessons learned. The magnet cooling down operation was initiated in late September 2016. The vacuum vessel was pumped out three weeks before the first plasma. The impregnation and curing of the two in-vessel divertor coils was performed at 180 °C during two days contributing to the baking of the vacuum vessel. In the meanwhile, rehearsal sessions for testing the CODAC systems were organized every month. The toroidal, poloidal, and divertor field coils were energized and their performance was tested successfully allowing moving to the first plasma operation phase. After a few attempts, plasma breakdown was achieved confirming that all systems were properly running and synchronized. Due to several micro air leaks on fiber optic feedthroughs and issues with the design of the in-vessel stabilizing plates, plasma current ramp-up could not be achieved in a first step. Once these issues have been fixed, confined plasmas could be obtained. Diverted plasmas were then achieved and the plasma current was increased up to 800 kA for more than 10 s. Up to 2.5 MW of additional power was eventually successfully coupled to the plasma.