After seven years of assembly, integrated commissioning will now start, checking in sequence the operation of each system, including evacuating the JT-60SA plasma chamber and cooling the superconducting coils, leading up to the first plasma operation expected in the autumn of 2020. The JT-60SA is designed to explore advanced plasma physics in general and to support of the planned operation of ITER and next-phase fusion devices.

JT-60SA is part of the Broader Approach, a joint program of fusion research and development agreed and co-financed by the European Atomic Energy Community (Euratom) and the government of Japan (represented by its Ministry of Education, Culture, Sports, Science and Technology, MEXT).

The JT-60SA replaces a tokamak experiment that operated at the Naka Fusion Institute from 1985 to 2008 (first as JT-60, then as JT-60U), and re-uses the site buildings, the neutral beam heating apparatus, and some power supplies and auxiliaries. All core machine components – including vacuum vessel, superconducting magnets, and surrounding cryostat – were re-designed and procured by the implementing teams, the National Institutes for Quantum and Radiological Science and Technology (QST, Japan) and European Domestic Agency for ITER, Fusion for Energy.

JT-60SA is capable of confining high-temperature deuterium plasmas for 100-second pulses, with a plasma current up to ~5.5 MA, a large amount of power available for plasma heating and current drive, and a water-cooled divertor designed for heat fluxes of 15 MW/m². It will be able to operate a wide range of plasma shapes (elongations and triangularities) and aspect ratios. With a plasma volume of ~130 m³, the device will take the lead as the world's largest operating tokamak ... until the operation of ITER, scheduled in 2025.

Its specific parameters will allow the team based in Naka to conduct research on key physics issues for ITER and the next-phase DEMO such as the development of optimized operational regimes; questions of stability and control, transport and confinement, and high-energy particle behaviour; pedestal and edge physics; plasma-material interaction; fusion engineering; and theoretical models and simulation codes.

Even before then, however, the experience of assembling, installing, commissioning and starting up JT-60SA will be highly valuable for the ITER. Thanks to a trilateral arrangement signed in November 2019 between the ITER Organization and the Broader Approach implementing agencies, the ITER Project will benefit from the knowledge and experience acquired by the development of the Broader Approach projects, and in particular JT-60SA. The trilateral arrangement foresees the exchange of data and information; the exchange of scientists, engineers and other technical experts; the exchange of equipment, materials and instrumentation; and jointly performed experimentation, including remote participation.

After the positioning of the cryostat top lid in March – the final task of main body assembly – ITER Director-General Bernard Bigot sent these words of congratulations: "Warmest congratulations to the team's successful completion of the JT-60SA tokamak. It is indeed a magnificent demonstration of QST capacity and of the collaboration established by Europe and Japan, to complete this critical milestone on time. We look forward to the first plasma on JT-60SA this autumn."

Broader Approach Extended

On 2 March, the European Atomic Energy Community (Euratom) and the Japanese government signed a joint declaration for the second phase of the Broader Approach activities, agreeing on further cooperation on research and development in the field of fusion energy. The tokamak programme activity will focus on the operation and exploitation of the recently assembled JT-60SA.

The new period 2020-2025 is the first operation phase of JT-60SA. In this phase JT-60SA will:

1. complete integrated commissioning including the first plasma, and evaluate the engineering achievements in constructing this large tokamak device,
2. execute plasma experiments for ITER risk mitigation, ITER scenario development, and study steady-state high pressure plasma operation requirements for DEMO, and
3. enhance the device capability to allow high-power heating experiments with deuterium.

For further information on JT-60SA visit: http://www.jt60sa.org