Mitigation of type-I ELMs with n=2 fields on JET with ITER-like wall
2013 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 53, no 7, 073036- p.Article in journal (Refereed) Published
Mitigation of type-I edge-localized modes (ELMs) was observed with the application of an n = 2 field in H-mode plasmas on the JET tokamak with the ITER-like wall (ILW). Several new findings with the ILW were identified and contrasted to the previous carbon wall (C-wall) results for comparable conditions. Previous results for high collisionality plasmas (nu*(e,ped) similar to 2.0) with the C-wall saw little or no influence of either n = 1 or n = 2 fields on the ELMs. However, recent observations with the ILW show large type-I ELMs with a frequency of similar to 45 Hz were replaced by high-frequency (similar to 200 Hz) small ELMs during the application of the n = 2 field. With the ILW, splitting of the outer strike point was observed for the first time during the strong mitigation of the type-I ELMs. The maximal surface temperature (T-max) on the outer divertor plate reached a stationary state and has only small variations of a few degrees due to the small mitigated ELMs. In moderate collisionality (nu*(e,ped) similar to 0.8) H-mode plasmas, similar to previous results with the C-wall, both an increase in the ELM frequency and density pump-out were observed during the application of the n = 2 field. There are two new observations compared with the C-wall results. Firstly, the effect of ELM mitigation with the n = 2 field was seen to saturate so that the ELM frequency did not further increase above a certain level of n = 2 magnetic perturbations. Secondly splitting of the outer strike point during the ELM crash was seen, resulting in mitigation of the maximal ELM peak heat fluxes on the divertor region.
Place, publisher, year, edition, pages
2013. Vol. 53, no 7, 073036- p.
Collisionality, Divertor region, Edgelocalized modes, High frequency HF, Magnetic perturbation, Small variations, Stationary state, Surface temperatures
IdentifiersURN: urn:nbn:se:kth:diva-126894DOI: 10.1088/0029-5515/53/7/073036ISI: 000321780500040ScopusID: 2-s2.0-84880168735OAI: oai:DiVA.org:kth-126894DiVA: diva2:642852
QC 201308232013-08-232013-08-222013-08-23Bibliographically approved