This title appears in the Scientific Report :
2011
Please use the identifier:
http://dx.doi.org/10.1088/0029-5515/51/7/073007 in citations.
Fuel retention in impurity seeded discharges in JET after Be evaporation
Fuel retention in impurity seeded discharges in JET after Be evaporation
Preparatory experiments for the ITER-Like Wall in JET were carried out to simulate the massive Be first wall by a thin Be layer, induced by evaporation of about 2.0 g Be, and to study its impact on fuel retention and divertor radiation with reduced C content and N seeding. Residual gas analysis reve...
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Personal Name(s): | Brezinsek, S. |
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Loarer, T. / Krieger, K. / Jachmich, S. / Tsalas, M. / Coffey, I. / Eich, T. / Fundamenski, W. / Giroud, C. / Grünhagen, S. / Huber, A. / Kruezi, U. / Knipe, S. / Maddision, G.P. / McCormick, K. / Meigs, A.G. / Morgan, Ph. / Philipps, V. / Sergienko, G. / Stagg, R. / Stamp, M.F. / Tabares, F.L. | |
Contributing Institute: |
Plasmaphysik; IEK-4 |
Published in: | Nuclear fusion, 51 (2011) S. 073007 |
Imprint: |
Vienna
IAEA
2011
|
Physical Description: |
073007 |
DOI: |
10.1088/0029-5515/51/7/073007 |
Document Type: |
Journal Article |
Research Program: |
Fusion |
Series Title: |
Nuclear Fusion
51 |
Subject (ZB): | |
Publikationsportal JuSER |
Preparatory experiments for the ITER-Like Wall in JET were carried out to simulate the massive Be first wall by a thin Be layer, induced by evaporation of about 2.0 g Be, and to study its impact on fuel retention and divertor radiation with reduced C content and N seeding. Residual gas analysis reveals a reduction of hydrocarbons by one order of magnitude and of O by a factor of 5 in the partial pressure owing to the evaporation. The evolution of wall conditions, impurity fluxes and divertor radiation have been studied in ELMy H-mode plasmas (B-t = 2.7T, I-p = 2.5 MA, P-aux = 16MW) whereas a non-seeded reference discharge was executed prior to the evaporation.The in situ measured Be flux at the midplane increased by about a factor of 40 whereas the C flux decreased by similar to 50% in the limiter phase of the first discharge with respect to the reference, but erosion of the Be layer and partial coverage with C takes place quickly. To make best use of the protective Be layer, only the first four discharges were employed for a gas balance analysis providing a D retention rate of 1.94 x 10(21) Ds(-1) which is comparable to rates with C walls. But the Be evaporation provides a non-saturated surface with respect to D and short term retention is not negligible in the balance; the measured retention is overestimated with respect to steady-state conditions like that of the ILW. Moreover, C was only moderately reduced and co-deposition of fuel with eroded Be and C occurs. The lower C content leads to a minor reduction in divertor radiation as the reference phase prior to seeding indicates. N adds to the radiation of D and the remaining C, and the N content rises due to the legacy effect which has been quantified by gas balance to be 30% of the injected N. C radiation increases with exposure time, and both contributors cause an increase in the radiated fraction in the divertor from 50% to 70%. The radiation pattern suggests that N dominates the increase in the first discharges though C is still the dominating radiator. Therefore, the validity of a proxy of the Be first wall by a thin Be layer is limited and restricted to plasma operation directly after the Be evaporation. |