Characterisation of plasma breakdown at JET with a carbon and ITER-like wall

P.C. de Vries, A.C.C. Sips, H.T. Kim, P.J. Lomas, F. Maviglia, R. Albanese, I. Coffey, E. Joffrin, M. Lehnen, A. Manzanares, M. O'Mulane, I. Nunes, G.J. van Rooij, F.G. Rimini, M.F. Stamp

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

The recent installation of a full metal, ITER-like, first wall provided the opportunity to study the impact of the plasma-facing materials on plasma initiation or breakdown. This study for the first time presents a full experimental characterisation of tokamak breakdown at JET, using all discharges since 2008, covering both operations with a main chamber carbon and a beryllium ITER-like main chamber wall. It was found that the avalanche phase was unaffected by the change in wall material. However, changes in out-gassing by the wall and lower carbon levels resulted in better controlled density and significantly lower radiation during the burn-through phase with the ITER-like wall. Breakdown failures, that usually developed with a carbon wall during the burn-through phase (especially after disruptions) were absent with the ITER-like wall. These observations match with the results obtained from a new model of plasma burn-through that includes plasma-surface interactions (Kim et al 2012 Nucl. Fusion 52 103016). This shows that chemical sputtering of carbon is the determining factor for the impurity content, and hence also radiation, during the burn-through phase for operations with a carbon wall. As seen experimentally, with a beryllium main wall, the plasma surface effects predicted by the model do not raise the radiation levels much above those expected for pure deuterium plasmas. With the ITER-like wall, operation with higher pre-fill pressures, and thus higher breakdown densities, was possible, which helped maintaining the density after breakdown.

LanguageEnglish
Article number053003
JournalNuclear Fusion
Volume53
Issue number5
DOIs
StatePublished - May 2013
Externally publishedYes

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breakdown
carbon
beryllium
radiation
chambers
deuterium plasma
avalanches
surface reactions
installing
coverings
fusion
sputtering
impurities
metals

Cite this

de Vries, P. C., Sips, A. C. C., Kim, H. T., Lomas, P. J., Maviglia, F., Albanese, R., ... Stamp, M. F. (2013). Characterisation of plasma breakdown at JET with a carbon and ITER-like wall. Nuclear Fusion, 53(5), [053003]. DOI: 10.1088/0029-5515/53/5/053003
de Vries, P.C. ; Sips, A.C.C. ; Kim, H.T. ; Lomas, P.J. ; Maviglia, F. ; Albanese, R. ; Coffey, I. ; Joffrin, E. ; Lehnen, M. ; Manzanares, A. ; O'Mulane, M. ; Nunes, I. ; van Rooij, G.J. ; Rimini, F.G. ; Stamp, M.F./ Characterisation of plasma breakdown at JET with a carbon and ITER-like wall. In: Nuclear Fusion. 2013 ; Vol. 53, No. 5.
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de Vries, PC, Sips, ACC, Kim, HT, Lomas, PJ, Maviglia, F, Albanese, R, Coffey, I, Joffrin, E, Lehnen, M, Manzanares, A, O'Mulane, M, Nunes, I, van Rooij, GJ, Rimini, FG & Stamp, MF 2013, 'Characterisation of plasma breakdown at JET with a carbon and ITER-like wall' Nuclear Fusion, vol. 53, no. 5, 053003. DOI: 10.1088/0029-5515/53/5/053003

Characterisation of plasma breakdown at JET with a carbon and ITER-like wall. / de Vries, P.C.; Sips, A.C.C.; Kim, H.T.; Lomas, P.J.; Maviglia, F.; Albanese, R.; Coffey, I.; Joffrin, E.; Lehnen, M.; Manzanares, A.; O'Mulane, M.; Nunes, I.; van Rooij, G.J.; Rimini, F.G.; Stamp, M.F.

In: Nuclear Fusion, Vol. 53, No. 5, 053003, 05.2013.

Research output: Contribution to journalArticleAcademicpeer-review

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AU - de Vries,P.C.

AU - Sips,A.C.C.

AU - Kim,H.T.

AU - Lomas,P.J.

AU - Maviglia,F.

AU - Albanese,R.

AU - Coffey,I.

AU - Joffrin,E.

AU - Lehnen,M.

AU - Manzanares,A.

AU - O'Mulane,M.

AU - Nunes,I.

AU - van Rooij,G.J.

AU - Rimini,F.G.

AU - Stamp,M.F.

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de Vries PC, Sips ACC, Kim HT, Lomas PJ, Maviglia F, Albanese R et al. Characterisation of plasma breakdown at JET with a carbon and ITER-like wall. Nuclear Fusion. 2013 May;53(5). 053003. Available from, DOI: 10.1088/0029-5515/53/5/053003