ICRF specific plasma wall interactions in JET with the ITER-like wall

Bobkov, V.; Arnoux, G.; Brezinsek, S.; Coenen, J. W.; Colas, L.; Clever, M.; Czarnecka, A.; Braun, F.; Dux, R.; Huber, A.; Jacquet, Philippe; Klepper, C. C.; Lerche, E.; Maggi, C. F.; Marcotte, Frédérick; Maslov, M.; Matthews, G. F.; Mayoral, M.‐L.; McCormick, K.; Meigs, A.; Milanesio, Daniele; Monakhov, I.; Neu, R.; Noterdaeme, Jean-Marie; Pütterich, T.; Rimini, F.; Rooj, G. Van; Sergienko, G.; Eester, D. Van

doi:10.1016/j.jnucmat.2013.01.044

Cited by 35 publications

(48 citation statements)

References 13 publications

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“…Experiments were carried out with JET-ILW directly comparing the response of a constant density L-mode plasma to equal amounts of neutral beam (NBI) and ICRH heating, Fig.7. This showed that the power radiated from inside the separatrix (bulk radiation) is much greater with ICRH [32], particularly at low plasma density. Despite this high power loss, it is interesting that the rise in plasma stored energy (not shown) is very similar in the two heating phases.…”

Section: Effect Of Heating Methods On Sourcesmentioning

confidence: 96%

“…There are tungsten coated tiles in recessed areas of the main chamber of JET-ILW but as yet there is no definite link established to these yet either although a significant W level is still seen in ICRH heated limiter discharges. The cause of the increased radiation during ICRH in JET-ILW remains the subject of ongoing investigation and analysis [32].…”

Section: Effect Of Heating Methods On Sourcesmentioning

confidence: 99%

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Plasma operation with an all metal first-wall: Comparison of an ITER-like wall with a carbon wall in JET

Matthews

Contributors

2013

Journal of Nuclear Materials

158

110

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Section: Effect Of Heating Methods On Sourcesmentioning

confidence: 96%

Section: Effect Of Heating Methods On Sourcesmentioning

confidence: 99%

Plasma operation with an all metal first-wall: Comparison of an ITER-like wall with a carbon wall in JET

Matthews

Contributors

2013

Journal of Nuclear Materials

158

110

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“…Nevertheless, the strong increase of the W content was unexpected because the antenna limiters are completely made out of Be. Moreover no significant increase of the W source in the divertor, neither at the strike point region nor at the baffle at the divertor entrance was observed, leaving the source yet unidentified [25]. In principle, a change in the (edge) transport could also lead to a higher W concentration, but this seems to be unlikely because copper, which is detected as a trace impurity, does not increase during ICRH.…”

Section: Impurity Sources and Contentmentioning

confidence: 92%

First operation with the JET International Thermonuclear Experimental Reactor-like wall

et al. 2013

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AbstrAct.To consolidate ITER design choices and prepare for its operation, JET has implemented ITER's plasma facing materials, namely Be at the main wall and W in the divertor. In addition, protection systems, diagnostics and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs), but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (Section 1factor 10) have led to much lower radiation during the plasma burn-through phase eliminating breakdown failures.Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D 2 /Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a reduced power threshold by 30%, a distinct minimum density and pronounced shape dependence. The L-mode density limit was found up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be only re-established when using gas puff levels of a few 10 21 es −1. On average the confinement is lower with the new PFCs, but nevertheless, H factors up to 1 (H-Mode) and 1.3 (at b N ≈ 3, hybrids) have been achieved withWconcentrationswell below themaximum acceptable level.

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“…However, the strong increase of the W content was unexpected because the antenna limiters in JET are completely made out of Be. Moreover no significant increase of the W source in the divertor, neither at the strike point region nor at the baffle at the divertor entrance was observed, leaving the source yet to be identified [49]. In principle, a change in the (edge) transport could also lead to a higher W concentration, but this seems to be unlikely because copper, which is detected as a trace impurity, does not increase during ICRH.…”

Section: E Icrh Compatibility With W Plasma Facing Componentsmentioning

confidence: 92%

“…A way forward will be the comparison of measured W source profiles with the results of sophisticated RF-codes in order to validate them. An important benchmark will be the reactivation of the JET ITER-like antennas in 2014, which are predicted to cause significantly less impurity influx in JET than the currently existing ones [49]. The H-Mode threshold is consistently reduced by ≈ 30% in AUG and JET.…”

Section: Summary and Conclusion For Itermentioning

confidence: 99%

Experiences With Tungsten Plasma Facing Components in ASDEX Upgrade and JET

Neu¹,

Brezinsek

Beurskens

et al. 2014

IEEE Trans. Plasma Sci.

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Abstract-ASDEX Upgrade (AUG) has been converted to all W plasma facing components (PFCs) in 2007 and JET has implemented the ITER like wall (ILW) project (2011) using the same PFC configuration as ITER during its active phase, namely Be in the main chamber and tungsten in the divertor. As a result of the all metal PFCs in both devices much less surface conditioning is needed to arrive at reproducible wall conditions. Specifically the Be PFCs of JET led to a very small low-Z content (reduction of C and O by at least a factor of 10), reducing the edge radiation in steady state operation as well as during disruptions. Both devices successfully employ massive gas injection to mitigate disruption forces and power loads to PFCs by radiating up to 100% of the available energy. Hydrogen retention is strongly reduced (AUG: factor 5, JET: factor 10) and the remaining retention is still dominated by co-deposition with residual C in AUG and intrinsic Be in JET. The very low edge and divertor radiation could be compensated by impurity seeding either by a single gas species (N2) (AUG and JET) or by combining N2 and Ar (AUG) injection for divertor and main chamber radiation, respectively. The W sputtering in the divertor increases when seeding small amounts of N2, but decreases for higher fluxes due to the plasma cooling provided by the nitrogen radiation. The tungsten content is controlled by the source as well as by its edge and central transport. It could be kept sufficiently small by using a minimum gas fuelling to reduce the W erosion and to diminish the W penetration. The control of the central W transport by central (wave) heating had been well established in AUG, however in both devices the W content is increased during ICRH operation most probably due to increased W sputtering caused by rectified sheaths. The H-Mode threshold is reduced by 20-30% in AUG and JET, but on average the confinement is lower in JET-ILW than with C PFCs. To date it is not yet clear, whether the reduced H-Mode confinement has to be attributed to the use of W PFCs, since such a clear trend as in JET was not found in AUG.

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ICRF specific plasma wall interactions in JET with the ITER-like wall

Cited by 35 publications

References 13 publications

Plasma operation with an all metal first-wall: Comparison of an ITER-like wall with a carbon wall in JET

Plasma operation with an all metal first-wall: Comparison of an ITER-like wall with a carbon wall in JET

First operation with the JET International Thermonuclear Experimental Reactor-like wall

Experiences With Tungsten Plasma Facing Components in ASDEX Upgrade and JET

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