Speaker
Description
See full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P5.1006.pdf
Disruption mitigation is one of the main research topics on the way to ITER and future Tokamak fusion power plants. Therefore, extensive studies have to be carried out on large Tokamaks to understand the physics and to develop the necessary technologies. JT-60SA, which will go into operation in 2020, will be a primary machine for this research. It will be equipped with a Massive Gas Injection (MGI) system to conduct disruption mitigation experiments in the first research phases. This MGI system will consist of two fast valves with integrated reservoirs (1000 cm³), which will be installed inside the vacuum vessel behind the stabilizing plate. The toroidally opposite locations in upper oblique position minimize the distance between the valves and the q=2 surface and maximizes the distance between the two injection spots. This setup allows investigation of radiation asymmetries, heat load and force mitigation in various plasma scenarios, runaway electron mitigation and gas propagation into hot plasmas. The close proximity of the valves to the plasma is especially beneficial for unstable scenarios like runaway beam mitigation. Each valve will be able to hold up to 7500 Pa*m³ of mitigation gas, that can be injected within milliseconds. Due to their location inside the vacuum vessel, the valves must be compatible with in-vessel conditions (magnetic field, elevated temperature, radiation and vacuum). Hence, a spring-driven valve with piezoelectric actuation was chosen as design basis. It is foreseen to inject a large variety of different noble gases and gas mixtures with H2/D2. A gas preparation system was specifically designed to allow mixing of different gases and fast filling of the MGI valves internal voluminal, while still complying with high safety standards regarding high pressures and explosion prevention. Finally, the vacuum feedthroughs were designed to preserve the different electric potentials of the machine and the vacuum conditions of the cryostat while allowing high pressure gas supply and 120 V trigger voltage to the MGI valves. This contribution presents the detailed designs of the MGI valves, the gas preparation system and the vacuum feedthroughs together with the results of the design analysis.
