Runaway electron beam control

D. Carnevale, JET Contributors, Tommy Ahlgren

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Post-disruption runaway electron (RE) beams in tokamaks with large current can cause deep melting of the vessel and are one of the major concerns for ITER operations. Consequently, a considerable effort is provided by the scientific community in order to test RE mitigation strategies. We present an overview of the results obtained at FTU and TCV controlling the current and position of RE beams to improve safety and repeatability of mitigation studies such as massive gas (MGI) and shattered pellet injections (SPI). We show that the proposed RE beam controller (REB-C) implemented at FTU and TCV is effective and that current reduction of the beam can be performed via the central solenoid reducing the energy of REs, providing an alternative/parallel mitigation strategy to MGI/SPI. Experimental results show that, meanwhile deuterium pellets injected on a fully formed RE beam are ablated but do not improve RE energy dissipation rate, heavy metals injected by a laser blow off system on low-density flat-top discharges with a high level of RE seeding seem to induce disruptions expelling REs. Instabilities during the RE beam plateau phase have shown to enhance losses of REs, expelled from the beam core. Then, with the aim of triggering instabilities to increase RE losses, an oscillating loop voltage has been tested on RE beam plateau phase at TCV revealing, for the first time, what seems to be a full conversion from runaway to ohmic current. We finally report progresses in the design of control strategies at JET in view of the incoming SPI mitigation experiments.

Original languageEnglish
Article number014036
JournalPlasma Physics and Controlled Fusion
Volume61
Issue number1
Number of pages8
ISSN0741-3335
DOIs
Publication statusPublished - Jan 2019
MoE publication typeA1 Journal article-refereed
EventEPS Conference on Plasma Physics - Praha, Czech Republic
Duration: 2 Jul 20186 Jul 2018
Conference number: 45

Fields of Science

  • FTU
  • magnetic confinement
  • plasma control system
  • runaways
  • 114 Physical sciences

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