Joffrin, and 240 co-authors, reported in 2019 that for the past several years, the JET scientific program has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology program was launched with a view to prepare the D–T campaign (DTE2).
The authors address the key elements developed by the JET program directly contributing to the D–T preparation. This intense preparation includes the review of the physics basis for the D–T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D–T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfvèn-eigenmode antennas, neutral gauges, radiation hard imaging systems…) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D–T campaign provides an incomparable source of information and a basis for the future D–T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
The authors concluded that JET experimental and analysis campaigns have strengthened the preparation of the next tritium and D–T campaigns. Both baseline and hybrid operational regimes have produced promising results (more than 7 MW of equivalent fusion power), while remaining compatible with the ILW. In support of the scenario a huge step forward in the understanding of the isotope physics has been achieved. This would not have been the case without a strong focus towards D–T. In addition, the operational preparation for the D–T phase has now reached a high-quality level, tackling issues that had not been addressed in non-tritium compatible device such as neutron calibration, tritium handling, isotope control, wall erosion, etc.
JET is uniquely placed to provide a robust base for burning plasmas during its future D–T phase. The shutdown required to prepare for deuterium–tritium operations is now complete and despite recent delays, JET is ready to move towards a new domain with the new D–T phase. The main campaign elements until the end of 2020 are as follows:
- A deuterium campaign for the preparation of high-performance scenarios and studies of disruption and runaway election mitigation using a new shatter-pellet injection system presently installed on JET as part of an ITER, EURATOM and US-DOE agreement.
- Hydrogen and 100% tritium campaigns combined with reference pulses in deuterium for the study of isotope effects.
- A deuterium–tritium campaign with the aim of producing 15 MW of fusion power for 5 s in stationary conditions in order to study the key physics aspects, such as those related to alpha particles, that a change from deuterium to a deuterium–tritium plasma may involve.
The JET program will provide invaluable information for the non-activated phase of ITER, alpha particle and isotopic effects in plasma scenarios, particle and heat transport, retention, and wall cleaning. In parallel to the preparation of the D–T phase, JET is developing a strong program in support of the ITER research plan for disruption mitigation with the new shattered pellet injector and radiative layer studies. All these efforts will ensure a maximized output to ITER operation from its first plasma to the D–T phase.
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