Development of internal transport barrier scenarios at ITER-relevant high triangularity in JET
The development of ITB scenarios in high triangularity discharges is of particular interest for ITER AT operation. Previous JET experiments have shown that high triangularity favours ELM-free or type I ELMs, which inhibit long lasting ITBs. The recent experiments reported here concentrate on integrated optimisation of edge and core conditions. Edge pedestal was controlled using gas injection, Deuterium or light impurities, and plasma current ramps. Both methods yield more ITB-friendly edge pedestal; conditions, varying from small type I to type III ELMs and, in extreme cases, to L-mode edge. In parallel, the conditions for triggering and sustaining a wide ITB, located in the reversed shear deeply reversed target current profiles with q(min)~3. A narrow inner ITB, located in the reversed shear region, is routinely observed. Large radius ITBs are only triggered when the input power exceeds 20-22 MW, but they do not usually survive the transmission into H-mode. The best results, in terms of sustained high performance, have been obtained with Neon injection: a wide ITB is triggred during the phase with L-mode edge and survives into H-mode for about 2s at H(89)beta(N) ~ 3.5 and ~60% of the Greenwald density limit.In summary, a high triangularity scenario has been developed, which combines the desirable characteristics of controlled edge, long lasting wide ITBs and high performance at density higher than the low triangularity JET scenarios.
Bibliographic Reference: An oral paper given at: 20th IAEA Fusion Energy Conference Organised by: International Atomic Energy Agency Held at: Centrtro de Fusao Nuclear, Vilamoura (PT)
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: firstname.lastname@example.org
Record Number: 200417779 / Last updated on: 2004-11-10
Original language: en
Available languages: en