Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET

G.P. Maddison, C. Giroud, B. Alper, G. Arnoux, I. Balboa, M.N.A. Beurskens, A. Boboc, S. Brezinsek, M. Brix, M. Clever, R. Coelho, J.W. Coenen, I. Coffey, P.C. da Silva Aresta Belo, S. Devaux, P. Devynck, T. Eich, R. C. Felton, J. Flanagan, L. Frassinetti & 30 others L. Garzotti, M. Groth, S. Jachmich, A. Jarvinen, E. Joffrin, M.A.H. Kempenaars, U. Kruezi, K. D. Lawson, M. Lehnen, M. J. Leyland, Y. Liu, P.J. Lomas, C.G. Lowry, S. Marsen, G.F. Matthews, G.K. McCormick, A.G. Meigs, A.W. Morris, R. Neu, I.M. Nunes, M. Oberkofler, F.G. Rimini, S. Saarelma, B. Sieglin, A.C.C. Sips, A. Sirinelli, M.F. Stamp, G.J. van Rooij, D.J. Ward, M. Wischmeier

Research output: Contribution to journalArticleAcademicpeer-review

14 Citations (Scopus)

Abstract

The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ≈ 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ≈30% lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard–outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D–T experiments on JET and for 'baseline' operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.
LanguageEnglish
Article number07316
Pages1-28
JournalNuclear Fusion
Volume54
Issue number7
DOIs
StatePublished - Jul 2014
Externally publishedYes

Keywords

  • JET
  • ITER
  • beryllium
  • tungsten
  • carbon

Cite this

Maddison, G. P., Giroud, C., Alper, B., Arnoux, G., Balboa, I., Beurskens, M. N. A., ... Wischmeier, M. (2014). Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET. Nuclear Fusion, 54(7), 1-28. [07316]. DOI: 10.1088/0029-5515/54/7/073016
Maddison, G.P. ; Giroud, C. ; Alper, B. ; Arnoux, G. ; Balboa, I. ; Beurskens, M.N.A. ; Boboc, A. ; Brezinsek, S. ; Brix, M. ; Clever, M. ; Coelho, R. ; Coenen, J.W. ; Coffey, I. ; da Silva Aresta Belo, P.C. ; Devaux, S. ; Devynck, P. ; Eich, T. ; Felton, R. C. ; Flanagan, J. ; Frassinetti, L. ; Garzotti, L. ; Groth, M. ; Jachmich, S. ; Jarvinen, A. ; Joffrin, E. ; Kempenaars, M.A.H. ; Kruezi, U. ; Lawson, K. D. ; Lehnen, M. ; Leyland, M. J. ; Liu, Y. ; Lomas, P.J. ; Lowry, C.G. ; Marsen, S. ; Matthews, G.F. ; McCormick, G.K. ; Meigs, A.G. ; Morris, A.W. ; Neu, R. ; Nunes, I.M. ; Oberkofler, M. ; Rimini, F.G. ; Saarelma, S. ; Sieglin, B. ; Sips, A.C.C. ; Sirinelli, A. ; Stamp, M.F. ; van Rooij, G.J. ; Ward, D.J. ; Wischmeier, M./ Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET. In: Nuclear Fusion. 2014 ; Vol. 54, No. 7. pp. 1-28
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title = "Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET",
abstract = "The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ≈ 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ≈30{\%} lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard–outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D–T experiments on JET and for 'baseline' operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.",
keywords = "JET, ITER, beryllium, tungsten, carbon",
author = "G.P. Maddison and C. Giroud and B. Alper and G. Arnoux and I. Balboa and M.N.A. Beurskens and A. Boboc and S. Brezinsek and M. Brix and M. Clever and R. Coelho and J.W. Coenen and I. Coffey and {da Silva Aresta Belo}, P.C. and S. Devaux and P. Devynck and T. Eich and Felton, {R. C.} and J. Flanagan and L. Frassinetti and L. Garzotti and M. Groth and S. Jachmich and A. Jarvinen and E. Joffrin and M.A.H. Kempenaars and U. Kruezi and Lawson, {K. D.} and M. Lehnen and Leyland, {M. J.} and Y. Liu and P.J. Lomas and C.G. Lowry and S. Marsen and G.F. Matthews and G.K. McCormick and A.G. Meigs and A.W. Morris and R. Neu and I.M. Nunes and M. Oberkofler and F.G. Rimini and S. Saarelma and B. Sieglin and A.C.C. Sips and A. Sirinelli and M.F. Stamp and {van Rooij}, G.J. and D.J. Ward and M. Wischmeier",
year = "2014",
month = "7",
doi = "10.1088/0029-5515/54/7/073016",
language = "English",
volume = "54",
pages = "1--28",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "Institute of Physics",
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Maddison, GP, Giroud, C, Alper, B, Arnoux, G, Balboa, I, Beurskens, MNA, Boboc, A, Brezinsek, S, Brix, M, Clever, M, Coelho, R, Coenen, JW, Coffey, I, da Silva Aresta Belo, PC, Devaux, S, Devynck, P, Eich, T, Felton, RC, Flanagan, J, Frassinetti, L, Garzotti, L, Groth, M, Jachmich, S, Jarvinen, A, Joffrin, E, Kempenaars, MAH, Kruezi, U, Lawson, KD, Lehnen, M, Leyland, MJ, Liu, Y, Lomas, PJ, Lowry, CG, Marsen, S, Matthews, GF, McCormick, GK, Meigs, AG, Morris, AW, Neu, R, Nunes, IM, Oberkofler, M, Rimini, FG, Saarelma, S, Sieglin, B, Sips, ACC, Sirinelli, A, Stamp, MF, van Rooij, GJ, Ward, DJ & Wischmeier, M 2014, 'Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET' Nuclear Fusion, vol. 54, no. 7, 07316, pp. 1-28. DOI: 10.1088/0029-5515/54/7/073016

Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET. / Maddison, G.P.; Giroud, C.; Alper, B.; Arnoux, G.; Balboa, I.; Beurskens, M.N.A.; Boboc, A.; Brezinsek, S.; Brix, M.; Clever, M.; Coelho, R.; Coenen, J.W.; Coffey, I.; da Silva Aresta Belo, P.C.; Devaux, S.; Devynck, P.; Eich, T.; Felton, R. C.; Flanagan, J.; Frassinetti, L.; Garzotti, L.; Groth, M.; Jachmich, S.; Jarvinen, A.; Joffrin, E.; Kempenaars, M.A.H.; Kruezi, U.; Lawson, K. D.; Lehnen, M.; Leyland, M. J.; Liu, Y.; Lomas, P.J.; Lowry, C.G.; Marsen, S.; Matthews, G.F.; McCormick, G.K.; Meigs, A.G.; Morris, A.W.; Neu, R.; Nunes, I.M.; Oberkofler, M.; Rimini, F.G.; Saarelma, S.; Sieglin, B.; Sips, A.C.C.; Sirinelli, A.; Stamp, M.F.; van Rooij, G.J.; Ward, D.J.; Wischmeier, M.

In: Nuclear Fusion, Vol. 54, No. 7, 07316, 07.2014, p. 1-28.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET

AU - Maddison,G.P.

AU - Giroud,C.

AU - Alper,B.

AU - Arnoux,G.

AU - Balboa,I.

AU - Beurskens,M.N.A.

AU - Boboc,A.

AU - Brezinsek,S.

AU - Brix,M.

AU - Clever,M.

AU - Coelho,R.

AU - Coenen,J.W.

AU - Coffey,I.

AU - da Silva Aresta Belo,P.C.

AU - Devaux,S.

AU - Devynck,P.

AU - Eich,T.

AU - Felton,R. C.

AU - Flanagan,J.

AU - Frassinetti,L.

AU - Garzotti,L.

AU - Groth,M.

AU - Jachmich,S.

AU - Jarvinen,A.

AU - Joffrin,E.

AU - Kempenaars,M.A.H.

AU - Kruezi,U.

AU - Lawson,K. D.

AU - Lehnen,M.

AU - Leyland,M. J.

AU - Liu,Y.

AU - Lomas,P.J.

AU - Lowry,C.G.

AU - Marsen,S.

AU - Matthews,G.F.

AU - McCormick,G.K.

AU - Meigs,A.G.

AU - Morris,A.W.

AU - Neu,R.

AU - Nunes,I.M.

AU - Oberkofler,M.

AU - Rimini,F.G.

AU - Saarelma,S.

AU - Sieglin,B.

AU - Sips,A.C.C.

AU - Sirinelli,A.

AU - Stamp,M.F.

AU - van Rooij,G.J.

AU - Ward,D.J.

AU - Wischmeier,M.

PY - 2014/7

Y1 - 2014/7

N2 - The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ≈ 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ≈30% lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard–outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D–T experiments on JET and for 'baseline' operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.

AB - The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ≈ 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ≈30% lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard–outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D–T experiments on JET and for 'baseline' operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.

KW - JET

KW - ITER

KW - beryllium

KW - tungsten

KW - carbon

U2 - 10.1088/0029-5515/54/7/073016

DO - 10.1088/0029-5515/54/7/073016

M3 - Article

VL - 54

SP - 1

EP - 28

JO - Nuclear Fusion

T2 - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 7

M1 - 07316

ER -

Maddison GP, Giroud C, Alper B, Arnoux G, Balboa I, Beurskens MNA et al. Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET. Nuclear Fusion. 2014 Jul;54(7):1-28. 07316. Available from, DOI: 10.1088/0029-5515/54/7/073016