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. Becker & 30 others K. 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, J. Likonen

Research output: Contribution to journalArticleScientificpeer-review

109 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 number12B
DOIs
Publication statusPublished - 14 Nov 2007
MoE publication typeA1 Journal article-refereed

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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

Cite this

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. ; Likonen, J. / Plasma wall interaction and its implication in an all tungsten divertor tokamak. In: Plasma Physics and Controlled Fusion. 2007 ; Vol. 49, No. 12B.
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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 J. Likonen",
year = "2007",
month = "11",
day = "14",
doi = "10.1088/0741-3335/49/12B/S04",
language = "English",
volume = "49",
journal = "Plasma Physics and Controlled Fusion",
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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 & Likonen, J 2007, 'Plasma wall interaction and its implication in an all tungsten divertor tokamak', Plasma Physics and Controlled Fusion, vol. 49, no. 12B. https://doi.org/10.1088/0741-3335/49/12B/S04

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.; Likonen, J.

In: Plasma Physics and Controlled Fusion, Vol. 49, No. 12B, 14.11.2007.

Research output: Contribution to journalArticleScientificpeer-review

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 - Likonen, J.

PY - 2007/11/14

Y1 - 2007/11/14

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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U2 - 10.1088/0741-3335/49/12B/S04

DO - 10.1088/0741-3335/49/12B/S04

M3 - Article

VL - 49

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 12B

ER -