Community Research and Development Information Service - CORDIS

Abstract

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 (beta(N) = 2) ELMy H-mode has been achieved by operating near the ITER triangularity (delta ~ 0.40�0.5) and safety factor (q(95) ~ 3), at Z(eff ) ~ 1.5�2. In advanced tokamak (AT) scenarios, internal transport barriers (ITBs) are now characterized in real time with a new criterion, roh*(T).

Tailoring of the current profile with 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. Alfvén 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 ~ 50% bootstrap current. A record duration of ITBs was achieved, up to 11s, 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

Additional information

Authors: PAMELA J, EFDA Close Support Unit, Culham Science Centre, Abingdon, Oxon (UK);SOLANO E R, EFDA Close Support Unit, Culham Science Centre, Abingdon, Oxon (UK)
Bibliographic Reference: An article published in: Nucl. Fusion 43 (2003) 1540�1554 PII: S0029-5515(03)68825-3
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: stacks.iop.org/NF/43/1540
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top