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KTH, Superseded Departments, Alfvén Laboratory.
KTH, Superseded Departments, Alfvén Laboratory.
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2003 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 43, no 12, 1540-1554 p.Article in journal (Refereed) Published
Abstract [en]

Scientific and technical activities on JET focus on the issues likely to affect the ITER design and operation. Our understanding of the ITER reference mode of operation, the ELMy H-mode, has progressed significantly. The extrapolation of ELM size to ITER has been re-evaluated. Neoclassical tearing modes have been shown to be meta-stable in JET, and their beta limits can be raised by destabilization (modification) of sawteeth by ion cyclotron radio frequency heating (ICRH). Alpha simulation experiments with ICRH accelerated injected 4 (He) beam ions provide a new tool for fast particle and magnetohydrodynamic studies, with up to 80-90% of plasma heating by fast 4 He ions. With or without impurity seeding, a quasi-steady-state high confinement (H-98 = 1), high density(n(e)/n(GW) = 0.9-1) and high beta (betaN = 2) ELMy H-mode has been achieved by operating near the ITER triangularity ( similar to 0.40-0.5) and safety factor (q(95) similar to 3), at Z(eff) similar to 1.5-2. In advanced tokamak (AT) scenarios, internal transport barriers (ITBs) are now characterized in real time with a new criterion, rhoT(*). Tailoring of the current profile with T lower hybrid current drive provides reliable access to a variety of q profiles, lowering access power for barrier formation. Rational q surfaces appear to be associated with ITB formation. Alfven cascades were observed in reversed shear plasmas, providing identification of q profile evolution. Plasmas with 'current holes' were observed and modelled. Transient high confinement AT regimes with H-89 = 3.3, beta(N) = 2.4 and ITER-relevant q < 5 were achieved with reversed magnetic shear. Quasi-stationary ITBs are developed with full non-inductive current drive, including similar to 50% bootstrap current. A record duration of ITBs was achieved, up to 11 s, approaching the resistive time. For the first time, pressure and current profiles of AT regimes are controlled by a real-time feedback system, in separate experiments. Erosion and co-deposition studies with a quartz micro-balance show reduced co-deposition. Measured divertor thermal loads during disruptions in JET could modify ITER assumptions.

Place, publisher, year, edition, pages
2003. Vol. 43, no 12, 1540-1554 p.
Keyword [en]
elmy h-modes internal transport barriers joint european torus current drive interaction issues tritium recovery plasma rotation high-density confinement shear
URN: urn:nbn:se:kth:diva-12481DOI: 10.1088/0029-5515/43/12/002ISI: 000187838300003OAI: diva2:315267
Artikeln har flera hundra författare. Enbart de två första och samtliga KTH-författare registrerade.Available from: 2010-04-28 Created: 2010-04-28 Last updated: 2010-10-27Bibliographically approved

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Hellsten, TorbjörnLaxåback, MartinRachlew, ElisabethRubel, Marek
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Alfvén LaboratoryPhysics
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