S. Higashijima

Heat and Particle Control in JT-60U

Heat and particle control has been studied under the reactor-relevant high-power heating in the large tokamak of JT-60U with an open divertor and progressively a W-shaped pumped divertor. Heat and particle control is crucial for reduction in heat load onto the divertor plates, control of density in the main plasma, effective exhaust of helium ash, and reduction in impurity contamination. For the reduction of heat load, radiative divertor concept was developed based on understanding of heat and particle transport in scrape-off layer and divertor plasmas, which contributed to establishment of divertor concept in ITER. With argon injection, the total radiation loss power reached up to 80% of the net heating power with high confinement of HHy2 ~ 1, where HHy2 is a confinement enhancement factor over the IPB98(y,2) ELMy H-mode scaling, at high density of 80% of the Greenwald density in the ELMy H-mode plasma. For the density control, the dependence of particle confinement on plasma parameters was systematically studied with two confinement times for center- and edge-fueled particles, which enabled discussion of density controllability. Core fueling using a high-field-side pellet injection extended the operation range of high confinement (HHy2 ~ 1) from 60 to 70% of the Greenwald density in the high βp ELMy H-mode plasma. Efficient helium ash exhaust of τHe*/τE = 2.8 was demonstrated in the ELMy H-mode plasma with the pumping from the private flux region, which is the same pumping geometry as that in ITER design. Reduction in Zeff by puff-and-pump scheme was demonstrated, and chemical sputtering yields were estimated with the consideration of not only methane but also heavier hydrocarbons. Their sputtering yields showed strong dependence on the wall temperature and weak dependence on the particle flux. The measured profiles of C II and C IV line intensities were well reproduced by the Monte Carlo impurity transport simulation code (IMPMC code). The estimation of sputtering yields and development of the simulation code enabled reliable predictions for impurity behavior in a fusion reactor.

Present Status of Manufacturing and R&Ds for the JT-60SA Tokamak

The JT-60SA superconducting tokamak is now under construction toward the first plasma in March 2019 as a joint project between the Broader Approach (BA) Satellite Tokamak Programme between Japan and Europe, and the Japanese national programme. The JT-60SA mission is to contribute to early realization of fusion energy by supporting ITER and by complementing ITER in resolving key physics and engineering issues for DEMO reactors. Before procurements of the major components, some R&Ds for key techniques were performed. By November 2014, 25 procurement arrangements (PAs) have been launched (JA: 14 PAs, EU: 11 PAs) covering 88% of the total cost of the BA Satellite Tokamak Programme, and the main components have entered the manufacturing stage. In addition, the JT-60SA tokamak assembly started since January 2013. This paper summarizes the recent progress of the JT-60SA project.