Overview of first JT-60SA plasma operation and plans in view of ITER and DEMO

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Abstract JT-60SA is the world’s largest superconducting tokamak in operation jointly built and exploited by Europe and Japan in the framework of the Broader Approach. JT-60SA aims at addressing some of the technological and physics challenges, such as the long pulse steady-state plasma operation at high beta. The start-up of JT-60SA, which culminated in the first JT-60SA plasma achieved on 23 October 2023 and Operation-1 (OP-1) until the end of 2023, including the achievement of >1 MA diverted plasmas, paves the way for a new generation of large superconducting tokamaks, such as ITER. Several key scientific topics were investigated during this initial phase. Similarly to ITER, the available parallel electric field ( E || ) is low and yet plasma initiation was quickly obtained by means of the trapped particle configuration (TPC) with the assistance of ∼1.5 MW of electron cyclotron resonance heating (ECRH). A first analysis and classification of the causes for disruptions have been done after the results of OP-1. Vertical displacement events (VDEs) were responsible for the vast majority of disruptions in increasing elongated plasmas, as the stabilization plate was not yet installed in this phase. Therefore, VDE predictors and control algorithms were developed using machine learning techniques with magnetics probe data, showing that these novel techniques are also suitable for the start-up tokamak phases characterized by scarce input data. JT-60SA will restart operation in 2026 following a series of upgrades. The experimental programme for future operations is guided by significant modelling ‘predict first’ activity, which shows that access to and development of H-mode in conditions of future burning plasmas will be possible with high negative neutral beam injection (N-NBI) and ECRH input power. The integration of such elements into a steady-state long pulse operation will be done with the installation of W plasma facing components (PFC) after the initial campaigns.

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