Transition to a regime of improved confinement in JET limiter dischargesFunded under: FP2-FUSION 10C
In the presence of auxiliary heating, JET plasmas bounded by a material limiter generally exhibit L-mode properties, i.e. lower energy confinement than with ohmic heating alone. At a given level of input power, significantly better confinement is obtained only with open divertor plasmas, when the H-mode regime is accessed. In limiter discharges, improved energy confinement has been transiently obtained in JET with pellet fuelling at the end of the current rise, when anomalous transport is strongly reduced in the plasma core. As this is a small volume region, however, the global enhancement is only approx. 10-20% above ordinary L-mode. This report describes new observations of a spontaneous transition to a regime of significantly improved limiter confinement (ILC), for both particles and energy, in JET discharges without magnetic separatrix and with low edge shear. The phenomenology of the transition is in many respects similar to that typical of H-modes, suggesting that a similar bifurcation mechanism may be at work.
Bibliographic Reference: Report: JET-P(91)40 EN (1991) 9 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199111645 / Last updated on: 1994-12-02
Original language: en
Available languages: en