Design of the Massive Gas Injection system for JT-60SA

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 (833 cm³, 7.5 MPa, 6247 Pa*m³, 1.5*1024 particles), which will be installed inside the vacuum vessel behind the stabilizing plate in sectors P09 and P18. 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 springdriven 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. CFD calculations were carried out to evaluate the gas flow from the valves into the vacuum vessel. This paper presents the detailed design of the MGI valves, a description of the in-vessel setup and the results of the CFD analysis.