On the Challenge of Plasma Heating with the JET Metallic Wall

TL;DR

This paper reviews the challenges and performance of JET's auxiliary heating systems with the new metallic wall, highlighting operational issues, modifications, and differences from previous carbon wall experiments.

Contribution

It provides a comprehensive analysis of the operation, modifications, and plasma behavior of NBI, ICRF, and LH systems in JET with the new metallic wall, comparing with previous carbon wall results.

Findings

Efficient plasma heating achieved with room for higher power.

Main issues included beam shine-through, RF-sheath heat loads, and arcing.

Differences in impurity content and heat loads compared to carbon wall.

Abstract

The major aspects linked to the use of the JET auxiliary heating systems: NBI, ICRF and LHCD, in the new JET ITER-like wall (JET-ILW) are presented. We show that although there were issues related to the operation of each system, efficient and safe plasma heating was obtained with room for higher power. For the NBI up to 25.7MW was safely injected; issues that had to be tackled were mainly the beam shine-through and beam re-ionisation before its entrance into the plasma. For the ICRF system, 5MW were coupled in L-mode and 4MW in H-mode; the main areas of concern were RF-sheaths related heat loads and impurities production. For the LH, 2.5 MW were delivered without problems; arcing and generation of fast electron beams in front of the launcher that can lead to high heat loads were the keys issues. For each system, an overview will be given of: the main modifications implemented for safe use, their compatibility with the new metallic wall, the differences in behavior compared with the previous carbon wall, with emphasis on heat loads and impurity content in the plasma.