• Energy Research

Nuclear materials and energy 37, 101521 - (2023). doi:10.1016/j.nme.2023.101521 Published by Elsevier, Amsterdam [u.a.]

Experimental studies of Deuterium and Tritium plasmas have been carried out at JET in the last years, yielding precious information for the next generation of fusion devices. Among the various approaches taken, JET's "Baseline" scenario experiments are pushing the machine towards its engineering limits by operating in a high-confinement H-mode at high toroidal field, plasma current and fuel density, as planned for ITER. The present paper provides a brief sketch of the Baseline scenario philosophy and discusses a number of RF-related results obtained in the preparation of the DT campaign as well as its preparations. Fusion powers of almost 9MW and energies of 12MJ have been reached in DT "Baseline" scenario plasmas. The differing role of radio frequency and beam heating is highlighted, the former allowing peaked core temperature profiles instrumental e.g. for core high-Z impurity chasing and the "landing" of high performance discharges while the latter is the main overall heating source in JET. Synergistic effects from the simultaneous use of wave and beam heating are responsible for a modest but noticeable increase in fusion power. One of the differences between D and DT plasmas is the plasma density, which impacts on the beam deposition as well as fast ion generation.

Nuclear materials and energy 38, 101587 - (2024). doi:10.1016/j.nme.2024.101587 Published by Elsevier, Amsterdam [u.a.]

Use of new 3-strap ICRF antennas with all-tungsten (W) limiters in ASDEX Upgrade results in a reduction of the W sources at the antenna limiters and of the W content in the confined plasma by at least a factor of 2 compared to the W-limiter 2-strap antennas used in the past. The reduction is observed with a broad range of plasma shapes. In multiple locations of antenna frame, the limiter W source has a minimum when RF image currents are decreased by cancellation of the RF current contributions of the central and the outer straps. In JET with ITER-like wall, ITER-like antenna produces about 20% less of main chamber radiation and of W content compared to the old A2 antennas. However the effect of the A2 antennas on W content is scattered depending on which antennas are powered. Experiments in JET with trace nitrogen (N 2 ) injection show that a presence of active ICRF antenna close to the midplane injection valve has little effect on the core N content, both in dipole and in -90 °phasing. This indicates that the effect of ICRF on impurity transport across the scape-off-layer is small in JET compared to the dominant effect on impurity sources leading to increased impurity levels during ICRF operation. EURATOM 633053 US Department of Energy DE-AC05-00OR22725