Beryllium migration in JET ITER-like wall plasmas

S. Brezinsek, A. Widdowson, M. Mayer, V. Philipps, P Baron-Wiechec, J.W. Coenen, K. Heinola, A. Huber, J. Likonen, P. Petersson, M. Rubel, M.F. Stamp, D. Borodin, J.P. Coad, A.G. Carrasco, A. Kirschner, S. Krat, K. Krieger, B. Lipschultz, Ch. Linsmeier & 3 others G.F. Matthews, K. Schmid, JET contributors

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38 Citations (Scopus)

Abstract

JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (Ein = 35 eV) and more than 100%, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.
Original languageEnglish
Article number063021
Number of pages10
JournalNuclear Fusion
Volume55
Issue number6
DOIs
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

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beryllium
erosion
sputtering
configurations
impurities
carbon
fiber composites
test stands
carbon fibers
guy wires
ducts
charge exchange
entrances
safety
dust
chambers
deposits
pumps
life (durability)
thresholds

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Brezinsek, S., Widdowson, A., Mayer, M., Philipps, V., Baron-Wiechec, P., Coenen, J. W., ... contributors, JET. (2015). Beryllium migration in JET ITER-like wall plasmas. Nuclear Fusion, 55(6), [063021]. https://doi.org/10.1088/0029-5515/55/6/063021
Brezinsek, S. ; Widdowson, A. ; Mayer, M. ; Philipps, V. ; Baron-Wiechec, P ; Coenen, J.W. ; Heinola, K. ; Huber, A. ; Likonen, J. ; Petersson, P. ; Rubel, M. ; Stamp, M.F. ; Borodin, D. ; Coad, J.P. ; Carrasco, A.G. ; Kirschner, A. ; Krat, S. ; Krieger, K. ; Lipschultz, B. ; Linsmeier, Ch. ; Matthews, G.F. ; Schmid, K. ; contributors, JET. / Beryllium migration in JET ITER-like wall plasmas. In: Nuclear Fusion. 2015 ; Vol. 55, No. 6.
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title = "Beryllium migration in JET ITER-like wall plasmas",
abstract = "JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4{\%} (Ein = 35 eV) and more than 100{\%}, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10{\%} is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25{\%} higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.",
author = "S. Brezinsek and A. Widdowson and M. Mayer and V. Philipps and P Baron-Wiechec and J.W. Coenen and K. Heinola and A. Huber and J. Likonen and P. Petersson and M. Rubel and M.F. Stamp and D. Borodin and J.P. Coad and A.G. Carrasco and A. Kirschner and S. Krat and K. Krieger and B. Lipschultz and Ch. Linsmeier and G.F. Matthews and K. Schmid and JET contributors",
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Brezinsek, S, Widdowson, A, Mayer, M, Philipps, V, Baron-Wiechec, P, Coenen, JW, Heinola, K, Huber, A, Likonen, J, Petersson, P, Rubel, M, Stamp, MF, Borodin, D, Coad, JP, Carrasco, AG, Kirschner, A, Krat, S, Krieger, K, Lipschultz, B, Linsmeier, C, Matthews, GF, Schmid, K & contributors, JET 2015, 'Beryllium migration in JET ITER-like wall plasmas', Nuclear Fusion, vol. 55, no. 6, 063021. https://doi.org/10.1088/0029-5515/55/6/063021

Beryllium migration in JET ITER-like wall plasmas. / Brezinsek, S.; Widdowson, A.; Mayer, M.; Philipps, V.; Baron-Wiechec, P; Coenen, J.W.; Heinola, K.; Huber, A.; Likonen, J.; Petersson, P.; Rubel, M.; Stamp, M.F.; Borodin, D.; Coad, J.P.; Carrasco, A.G.; Kirschner, A.; Krat, S.; Krieger, K.; Lipschultz, B.; Linsmeier, Ch.; Matthews, G.F.; Schmid, K.; contributors, JET.

In: Nuclear Fusion, Vol. 55, No. 6, 063021, 2015.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Beryllium migration in JET ITER-like wall plasmas

AU - Brezinsek, S.

AU - Widdowson, A.

AU - Mayer, M.

AU - Philipps, V.

AU - Baron-Wiechec, P

AU - Coenen, J.W.

AU - Heinola, K.

AU - Huber, A.

AU - Likonen, J.

AU - Petersson, P.

AU - Rubel, M.

AU - Stamp, M.F.

AU - Borodin, D.

AU - Coad, J.P.

AU - Carrasco, A.G.

AU - Kirschner, A.

AU - Krat, S.

AU - Krieger, K.

AU - Lipschultz, B.

AU - Linsmeier, Ch.

AU - Matthews, G.F.

AU - Schmid, K.

AU - contributors, JET

N1 - Project code: 104445

PY - 2015

Y1 - 2015

N2 - JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (Ein = 35 eV) and more than 100%, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.

AB - JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (Ein = 35 eV) and more than 100%, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.

U2 - 10.1088/0029-5515/55/6/063021

DO - 10.1088/0029-5515/55/6/063021

M3 - Article

VL - 55

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 6

M1 - 063021

ER -

Brezinsek S, Widdowson A, Mayer M, Philipps V, Baron-Wiechec P, Coenen JW et al. Beryllium migration in JET ITER-like wall plasmas. Nuclear Fusion. 2015;55(6). 063021. https://doi.org/10.1088/0029-5515/55/6/063021