ELM pacing investigations at JET with the new pellet launcher

TitleELM pacing investigations at JET with the new pellet launcher
Publication TypeJournal Article
Year of Publication2011
AuthorsP.T Lang, A. Alonso, B. Alper, E. Belonohy, A. Boboc, S. Devaux, T. Eich, D. Frigione, K. Gal, L. Garzotti, A. Geraud, G. Kocsis, F. Kochl, K. Lackner, A. Loarte, P.J Lomas, M. Maraschek, H.W Muller, R. Neu, J. Neuhauser, G. Petravich, G. Saibene, J. Schweinzer, H. Thomsen, M. Tsalas, R. Wenninger, H. Zohm
JournalNuclear Fusion
Volume51
Issue3
Number3
Pagination033010
Date PublishedMar
Type of ArticleArticle
ISBN Number0029-5515
KeywordsASDEX UPGRADE, ENERGY, INJECTION, ITER, LOSSES, MODE
Abstract

A new pellet injection system was installed at JET designed for both fuelling and ELM pacing. The purpose of the pacing section was to validate pellet ELM pacing as a suitable tool for ELM mitigation in ITER. Pellet pacing was confirmed at the large size scale of JET. The dynamics of triggered ELMs was investigated with respect to their spontaneous counterparts. Triggered ELMs show features also typical for spontaneous ELMs in several operational regimes. Since none of these regimes was unsettled by the pellets this is a strong hint for compatibility with other plasma control tools. Observations and modelling results indicate the ELM triggering occurs by the evolution of the pellet ablation plasmoid into the first ELM filament followed by a poloidal spread of the instability. An ELM obviously can be forced by a pellet due to the strong local perturbation imposed already under unusual onset conditions but then evolves like any ELM typical for the corresponding plasma regime. For tool optimization the pellet mass and hence the convective confinement losses imposed have to be minimized. In our experiments, a lower mass threshold was observed for the first time. It has been found that to reliably trigger an ELM the pellet needs to be sufficiently large (and fast) to penetrate close to the pedestal top. Recent investigations are clear steps forward to validate the pellet pacing approach for ITER.

DOI10.1088/0029-5515/51/3/033010
Division

FP

Department

PDG

PID

506bca96c5637433dac75b877a0bcc14

Alternate TitleNucl. Fusion

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