Plasma wall interaction and its implication in an all tungsten divertor tokamak

R. Neu, M. Balden, V. Bobkov, R. Dux, O. Gruber, A. Herrmann, A. Kallenbach, M. Kaufmann, C. F. Maggi, H. Maier, H. W. Müller, T. Pütterich, R. Pugno, V. Rohde, A. C C Sips, J. Stober, W. Suttrop, C. Angioni, C. V. Atanasiu, W. BeckerK. Behler, K. Behringer, A. Bergmann, T. Bertoncelli, R. Bilato, A. Bottino, M. Brambilla, F. Braun, A. Buhler, A. Chankin, G. Conway, D. P. Coster, P. De Marné, S. Dietrich, K. Dimova, R. Drube, T. Eich, K. Engelhardt, H. U. Fahrbach, U. Fantz, L. Fattorini, J. Fink, R. Fischer, A. Flaws, P. Franzen, J. C. Fuchs, K. Gàl, M. García Mũoz, M. Gemisic-Adamov, L. Giannone, S. Gori, S. Da Graca, H. Greuner, A. Gude, S. Günter, G. Haas, J. Harhausen, B. Heinemann, N. Hicks, J. Hobirk, D. Holtum, C. Hopf, L. Horton, M. Huart, V. Igochine, S. Kálvin, O. Kardaun, M. Kick, G. Kocsis, H. Kollotzek, C. Konz, K. Krieger, T. Kurki-Suonio, B. Kurzan, K. Lackner, P. T. Lang, P. Lauber, M. Laux, J. Likonen, L. Liu, A. Lohs, K. Mank, A. Manini, M. E. Manso, M. Maraschek, P. Martin, Y. Martin, M. Mayer, P. McCarthy, K. McCormick, H. Meister, F. Meo, P. Merkel, R. Merkel, V. Mertens, F. Merz, H. Meyer, M. Mlynek, F. Monaco, H. Murmann, G. Neu, J. Neuhauser, B. Nold, J. M. Noterdaeme, G. Pautasso, G. Pereverzev, E. Poli, M. Püschel, G. Raupp, M. Reich, B. Reiter, T. Ribeiro, R. Riedl, J. Roth, M. Rott, F. Ryter, W. Sandmann, J. Santos, K. Sassenberg, A. Scarabosio, G. Schall, J. Schirmer, A. Schmid, W. Schneider, G. Schramm, R. Schrittwieser, W. Schustereder, J. Schweinzer, S. Schweizer, B. Scott, U. Seidel, F. Serra, M. Sertoli, A. Sigalov, A. Silva, E. Speth, A. Stäbler, K. H. Steuer, E. Strumberger, G. Tardini, C. Tichmann, W. Treutterer, C. Tröster, L. Urso, E. Vainonen-Ahlgren, P. Varela, L. Vermare, D. Wagner, M. Wischmeier, E. Wolfrum, E. Würsching, D. Yadikin, Q. Yu, D. Zasche, T. Zehetbauer, M. Zilker, H. Zohm

Research output: Contribution to journalArticle

110 Citations (Scopus)

Abstract

ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.

Original languageEnglish
JournalPlasma Physics and Controlled Fusion
Volume49
Issue number12 B
DOIs
Publication statusPublished - Dec 1 2007

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Beam plasma interactions
Tungsten
tungsten
conditioning
Plasmas
antennas
interactions
Antennas
tiles
power loss
Glow discharges
Tile
glow discharges
shot
erosion
low concentrations
Erosion
Graphite
graphite
chambers

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Condensed Matter Physics
  • Nuclear and High Energy Physics

Cite this

Plasma wall interaction and its implication in an all tungsten divertor tokamak. / Neu, R.; Balden, M.; Bobkov, V.; Dux, R.; Gruber, O.; Herrmann, A.; Kallenbach, A.; Kaufmann, M.; Maggi, C. F.; Maier, H.; Müller, H. W.; Pütterich, T.; Pugno, R.; Rohde, V.; Sips, A. C C; Stober, J.; Suttrop, W.; Angioni, C.; Atanasiu, C. V.; Becker, W.; Behler, K.; Behringer, K.; Bergmann, A.; Bertoncelli, T.; Bilato, R.; Bottino, A.; Brambilla, M.; Braun, F.; Buhler, A.; Chankin, A.; Conway, G.; Coster, D. P.; De Marné, P.; Dietrich, S.; Dimova, K.; Drube, R.; Eich, T.; Engelhardt, K.; Fahrbach, H. U.; Fantz, U.; Fattorini, L.; Fink, J.; Fischer, R.; Flaws, A.; Franzen, P.; Fuchs, J. C.; Gàl, K.; Mũoz, M. García; Gemisic-Adamov, M.; Giannone, L.; Gori, S.; Da Graca, S.; Greuner, H.; Gude, A.; Günter, S.; Haas, G.; Harhausen, J.; Heinemann, B.; Hicks, N.; Hobirk, J.; Holtum, D.; Hopf, C.; Horton, L.; Huart, M.; Igochine, V.; Kálvin, S.; Kardaun, O.; Kick, M.; Kocsis, G.; Kollotzek, H.; Konz, C.; Krieger, K.; Kurki-Suonio, T.; Kurzan, B.; Lackner, K.; Lang, P. T.; Lauber, P.; Laux, M.; Likonen, J.; Liu, L.; Lohs, A.; Mank, K.; Manini, A.; Manso, M. E.; Maraschek, M.; Martin, P.; Martin, Y.; Mayer, M.; McCarthy, P.; McCormick, K.; Meister, H.; Meo, F.; Merkel, P.; Merkel, R.; Mertens, V.; Merz, F.; Meyer, H.; Mlynek, M.; Monaco, F.; Murmann, H.; Neu, G.; Neuhauser, J.; Nold, B.; Noterdaeme, J. M.; Pautasso, G.; Pereverzev, G.; Poli, E.; Püschel, M.; Raupp, G.; Reich, M.; Reiter, B.; Ribeiro, T.; Riedl, R.; Roth, J.; Rott, M.; Ryter, F.; Sandmann, W.; Santos, J.; Sassenberg, K.; Scarabosio, A.; Schall, G.; Schirmer, J.; Schmid, A.; Schneider, W.; Schramm, G.; Schrittwieser, R.; Schustereder, W.; Schweinzer, J.; Schweizer, S.; Scott, B.; Seidel, U.; Serra, F.; Sertoli, M.; Sigalov, A.; Silva, A.; Speth, E.; Stäbler, A.; Steuer, K. H.; Strumberger, E.; Tardini, G.; Tichmann, C.; Treutterer, W.; Tröster, C.; Urso, L.; Vainonen-Ahlgren, E.; Varela, P.; Vermare, L.; Wagner, D.; Wischmeier, M.; Wolfrum, E.; Würsching, E.; Yadikin, D.; Yu, Q.; Zasche, D.; Zehetbauer, T.; Zilker, M.; Zohm, H.

In: Plasma Physics and Controlled Fusion, Vol. 49, No. 12 B, 01.12.2007.

Research output: Contribution to journalArticle

Neu, R, Balden, M, Bobkov, V, Dux, R, Gruber, O, Herrmann, A, Kallenbach, A, Kaufmann, M, Maggi, CF, Maier, H, Müller, HW, Pütterich, T, Pugno, R, Rohde, V, Sips, ACC, Stober, J, Suttrop, W, Angioni, C, Atanasiu, CV, Becker, W, Behler, K, Behringer, K, Bergmann, A, Bertoncelli, T, Bilato, R, Bottino, A, Brambilla, M, Braun, F, Buhler, A, Chankin, A, Conway, G, Coster, DP, De Marné, P, Dietrich, S, Dimova, K, Drube, R, Eich, T, Engelhardt, K, Fahrbach, HU, Fantz, U, Fattorini, L, Fink, J, Fischer, R, Flaws, A, Franzen, P, Fuchs, JC, Gàl, K, Mũoz, MG, Gemisic-Adamov, M, Giannone, L, Gori, S, Da Graca, S, Greuner, H, Gude, A, Günter, S, Haas, G, Harhausen, J, Heinemann, B, Hicks, N, Hobirk, J, Holtum, D, Hopf, C, Horton, L, Huart, M, Igochine, V, Kálvin, S, Kardaun, O, Kick, M, Kocsis, G, Kollotzek, H, Konz, C, Krieger, K, Kurki-Suonio, T, Kurzan, B, Lackner, K, Lang, PT, Lauber, P, Laux, M, Likonen, J, Liu, L, Lohs, A, Mank, K, Manini, A, Manso, ME, Maraschek, M, Martin, P, Martin, Y, Mayer, M, McCarthy, P, McCormick, K, Meister, H, Meo, F, Merkel, P, Merkel, R, Mertens, V, Merz, F, Meyer, H, Mlynek, M, Monaco, F, Murmann, H, Neu, G, Neuhauser, J, Nold, B, Noterdaeme, JM, Pautasso, G, Pereverzev, G, Poli, E, Püschel, M, Raupp, G, Reich, M, Reiter, B, Ribeiro, T, Riedl, R, Roth, J, Rott, M, Ryter, F, Sandmann, W, Santos, J, Sassenberg, K, Scarabosio, A, Schall, G, Schirmer, J, Schmid, A, Schneider, W, Schramm, G, Schrittwieser, R, Schustereder, W, Schweinzer, J, Schweizer, S, Scott, B, Seidel, U, Serra, F, Sertoli, M, Sigalov, A, Silva, A, Speth, E, Stäbler, A, Steuer, KH, Strumberger, E, Tardini, G, Tichmann, C, Treutterer, W, Tröster, C, Urso, L, Vainonen-Ahlgren, E, Varela, P, Vermare, L, Wagner, D, Wischmeier, M, Wolfrum, E, Würsching, E, Yadikin, D, Yu, Q, Zasche, D, Zehetbauer, T, Zilker, M & Zohm, H 2007, 'Plasma wall interaction and its implication in an all tungsten divertor tokamak', Plasma Physics and Controlled Fusion, vol. 49, no. 12 B. https://doi.org/10.1088/0741-3335/49/12B/S04
Neu, R. ; Balden, M. ; Bobkov, V. ; Dux, R. ; Gruber, O. ; Herrmann, A. ; Kallenbach, A. ; Kaufmann, M. ; Maggi, C. F. ; Maier, H. ; Müller, H. W. ; Pütterich, T. ; Pugno, R. ; Rohde, V. ; Sips, A. C C ; Stober, J. ; Suttrop, W. ; Angioni, C. ; Atanasiu, C. V. ; Becker, W. ; Behler, K. ; Behringer, K. ; Bergmann, A. ; Bertoncelli, T. ; Bilato, R. ; Bottino, A. ; Brambilla, M. ; Braun, F. ; Buhler, A. ; Chankin, A. ; Conway, G. ; Coster, D. P. ; De Marné, P. ; Dietrich, S. ; Dimova, K. ; Drube, R. ; Eich, T. ; Engelhardt, K. ; Fahrbach, H. U. ; Fantz, U. ; Fattorini, L. ; Fink, J. ; Fischer, R. ; Flaws, A. ; Franzen, P. ; Fuchs, J. C. ; Gàl, K. ; Mũoz, M. García ; Gemisic-Adamov, M. ; Giannone, L. ; Gori, S. ; Da Graca, S. ; Greuner, H. ; Gude, A. ; Günter, S. ; Haas, G. ; Harhausen, J. ; Heinemann, B. ; Hicks, N. ; Hobirk, J. ; Holtum, D. ; Hopf, C. ; Horton, L. ; Huart, M. ; Igochine, V. ; Kálvin, S. ; Kardaun, O. ; Kick, M. ; Kocsis, G. ; Kollotzek, H. ; Konz, C. ; Krieger, K. ; Kurki-Suonio, T. ; Kurzan, B. ; Lackner, K. ; Lang, P. T. ; Lauber, P. ; Laux, M. ; Likonen, J. ; Liu, L. ; Lohs, A. ; Mank, K. ; Manini, A. ; Manso, M. E. ; Maraschek, M. ; Martin, P. ; Martin, Y. ; Mayer, M. ; McCarthy, P. ; McCormick, K. ; Meister, H. ; Meo, F. ; Merkel, P. ; Merkel, R. ; Mertens, V. ; Merz, F. ; Meyer, H. ; Mlynek, M. ; Monaco, F. ; Murmann, H. ; Neu, G. ; Neuhauser, J. ; Nold, B. ; Noterdaeme, J. M. ; Pautasso, G. ; Pereverzev, G. ; Poli, E. ; Püschel, M. ; Raupp, G. ; Reich, M. ; Reiter, B. ; Ribeiro, T. ; Riedl, R. ; Roth, J. ; Rott, M. ; Ryter, F. ; Sandmann, W. ; Santos, J. ; Sassenberg, K. ; Scarabosio, A. ; Schall, G. ; Schirmer, J. ; Schmid, A. ; Schneider, W. ; Schramm, G. ; Schrittwieser, R. ; Schustereder, W. ; Schweinzer, J. ; Schweizer, S. ; Scott, B. ; Seidel, U. ; Serra, F. ; Sertoli, M. ; Sigalov, A. ; Silva, A. ; Speth, E. ; Stäbler, A. ; Steuer, K. H. ; Strumberger, E. ; Tardini, G. ; Tichmann, C. ; Treutterer, W. ; Tröster, C. ; Urso, L. ; Vainonen-Ahlgren, E. ; Varela, P. ; Vermare, L. ; Wagner, D. ; Wischmeier, M. ; Wolfrum, E. ; Würsching, E. ; Yadikin, D. ; Yu, Q. ; Zasche, D. ; Zehetbauer, T. ; Zilker, M. ; Zohm, H. / Plasma wall interaction and its implication in an all tungsten divertor tokamak. In: Plasma Physics and Controlled Fusion. 2007 ; Vol. 49, No. 12 B.
@article{7b73d9794ffc4d38a3fd7952ba6b0b90,
title = "Plasma wall interaction and its implication in an all tungsten divertor tokamak",
abstract = "ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.",
author = "R. Neu and M. Balden and V. Bobkov and R. Dux and O. Gruber and A. Herrmann and A. Kallenbach and M. Kaufmann and Maggi, {C. F.} and H. Maier and M{\"u}ller, {H. W.} and T. P{\"u}tterich and R. Pugno and V. Rohde and Sips, {A. C C} and J. Stober and W. Suttrop and C. Angioni and Atanasiu, {C. V.} and W. Becker and K. Behler and K. Behringer and A. Bergmann and T. Bertoncelli and R. Bilato and A. Bottino and M. Brambilla and F. Braun and A. Buhler and A. Chankin and G. Conway and Coster, {D. P.} and {De Marn{\'e}}, P. and S. Dietrich and K. Dimova and R. Drube and T. Eich and K. Engelhardt and Fahrbach, {H. U.} and U. Fantz and L. Fattorini and J. Fink and R. Fischer and A. Flaws and P. Franzen and Fuchs, {J. C.} and K. G{\`a}l and Mũoz, {M. Garc{\'i}a} and M. Gemisic-Adamov and L. Giannone and S. Gori and {Da Graca}, S. and H. Greuner and A. Gude and S. G{\"u}nter and G. Haas and J. Harhausen and B. Heinemann and N. Hicks and J. Hobirk and D. Holtum and C. Hopf and L. Horton and M. Huart and V. Igochine and S. K{\'a}lvin and O. Kardaun and M. Kick and G. Kocsis and H. Kollotzek and C. Konz and K. Krieger and T. Kurki-Suonio and B. Kurzan and K. Lackner and Lang, {P. T.} and P. Lauber and M. Laux and J. Likonen and L. Liu and A. Lohs and K. Mank and A. Manini and Manso, {M. E.} and M. Maraschek and P. Martin and Y. Martin and M. Mayer and P. McCarthy and K. McCormick and H. Meister and F. Meo and P. Merkel and R. Merkel and V. Mertens and F. Merz and H. Meyer and M. Mlynek and F. Monaco and H. Murmann and G. Neu and J. Neuhauser and B. Nold and Noterdaeme, {J. M.} and G. Pautasso and G. Pereverzev and E. Poli and M. P{\"u}schel and G. Raupp and M. Reich and B. Reiter and T. Ribeiro and R. Riedl and J. Roth and M. Rott and F. Ryter and W. Sandmann and J. Santos and K. Sassenberg and A. Scarabosio and G. Schall and J. Schirmer and A. Schmid and W. Schneider and G. Schramm and R. Schrittwieser and W. Schustereder and J. Schweinzer and S. Schweizer and B. Scott and U. Seidel and F. Serra and M. Sertoli and A. Sigalov and A. Silva and E. Speth and A. St{\"a}bler and Steuer, {K. H.} and E. Strumberger and G. Tardini and C. Tichmann and W. Treutterer and C. Tr{\"o}ster and L. Urso and E. Vainonen-Ahlgren and P. Varela and L. Vermare and D. Wagner and M. Wischmeier and E. Wolfrum and E. W{\"u}rsching and D. Yadikin and Q. Yu and D. Zasche and T. Zehetbauer and M. Zilker and H. Zohm",
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TY - JOUR

T1 - Plasma wall interaction and its implication in an all tungsten divertor tokamak

AU - Neu, R.

AU - Balden, M.

AU - Bobkov, V.

AU - Dux, R.

AU - Gruber, O.

AU - Herrmann, A.

AU - Kallenbach, A.

AU - Kaufmann, M.

AU - Maggi, C. F.

AU - Maier, H.

AU - Müller, H. W.

AU - Pütterich, T.

AU - Pugno, R.

AU - Rohde, V.

AU - Sips, A. C C

AU - Stober, J.

AU - Suttrop, W.

AU - Angioni, C.

AU - Atanasiu, C. V.

AU - Becker, W.

AU - Behler, K.

AU - Behringer, K.

AU - Bergmann, A.

AU - Bertoncelli, T.

AU - Bilato, R.

AU - Bottino, A.

AU - Brambilla, M.

AU - Braun, F.

AU - Buhler, A.

AU - Chankin, A.

AU - Conway, G.

AU - Coster, D. P.

AU - De Marné, P.

AU - Dietrich, S.

AU - Dimova, K.

AU - Drube, R.

AU - Eich, T.

AU - Engelhardt, K.

AU - Fahrbach, H. U.

AU - Fantz, U.

AU - Fattorini, L.

AU - Fink, J.

AU - Fischer, R.

AU - Flaws, A.

AU - Franzen, P.

AU - Fuchs, J. C.

AU - Gàl, K.

AU - Mũoz, M. García

AU - Gemisic-Adamov, M.

AU - Giannone, L.

AU - Gori, S.

AU - Da Graca, S.

AU - Greuner, H.

AU - Gude, A.

AU - Günter, S.

AU - Haas, G.

AU - Harhausen, J.

AU - Heinemann, B.

AU - Hicks, N.

AU - Hobirk, J.

AU - Holtum, D.

AU - Hopf, C.

AU - Horton, L.

AU - Huart, M.

AU - Igochine, V.

AU - Kálvin, S.

AU - Kardaun, O.

AU - Kick, M.

AU - Kocsis, G.

AU - Kollotzek, H.

AU - Konz, C.

AU - Krieger, K.

AU - Kurki-Suonio, T.

AU - Kurzan, B.

AU - Lackner, K.

AU - Lang, P. T.

AU - Lauber, P.

AU - Laux, M.

AU - Likonen, J.

AU - Liu, L.

AU - Lohs, A.

AU - Mank, K.

AU - Manini, A.

AU - Manso, M. E.

AU - Maraschek, M.

AU - Martin, P.

AU - Martin, Y.

AU - Mayer, M.

AU - McCarthy, P.

AU - McCormick, K.

AU - Meister, H.

AU - Meo, F.

AU - Merkel, P.

AU - Merkel, R.

AU - Mertens, V.

AU - Merz, F.

AU - Meyer, H.

AU - Mlynek, M.

AU - Monaco, F.

AU - Murmann, H.

AU - Neu, G.

AU - Neuhauser, J.

AU - Nold, B.

AU - Noterdaeme, J. M.

AU - Pautasso, G.

AU - Pereverzev, G.

AU - Poli, E.

AU - Püschel, M.

AU - Raupp, G.

AU - Reich, M.

AU - Reiter, B.

AU - Ribeiro, T.

AU - Riedl, R.

AU - Roth, J.

AU - Rott, M.

AU - Ryter, F.

AU - Sandmann, W.

AU - Santos, J.

AU - Sassenberg, K.

AU - Scarabosio, A.

AU - Schall, G.

AU - Schirmer, J.

AU - Schmid, A.

AU - Schneider, W.

AU - Schramm, G.

AU - Schrittwieser, R.

AU - Schustereder, W.

AU - Schweinzer, J.

AU - Schweizer, S.

AU - Scott, B.

AU - Seidel, U.

AU - Serra, F.

AU - Sertoli, M.

AU - Sigalov, A.

AU - Silva, A.

AU - Speth, E.

AU - Stäbler, A.

AU - Steuer, K. H.

AU - Strumberger, E.

AU - Tardini, G.

AU - Tichmann, C.

AU - Treutterer, W.

AU - Tröster, C.

AU - Urso, L.

AU - Vainonen-Ahlgren, E.

AU - Varela, P.

AU - Vermare, L.

AU - Wagner, D.

AU - Wischmeier, M.

AU - Wolfrum, E.

AU - Würsching, E.

AU - Yadikin, D.

AU - Yu, Q.

AU - Zasche, D.

AU - Zehetbauer, T.

AU - Zilker, M.

AU - Zohm, H.

PY - 2007/12/1

Y1 - 2007/12/1

N2 - ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.

AB - ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.

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M3 - Article

AN - SCOPUS:36348999132

VL - 49

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 12 B

ER -