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The ion-cyclotron resonance heating of monster sawtooth and pellet-fuelled peaked-density profile in limiter discharges of JET tokamak are studied. The monster sawtooth is related to fast ions generated during the minority ion heating. In this regime, the global energy confinement is improved by about 20% over the sawteething discharges. In the ICRF heating of peaked-density profile discharges, typically, T(i0) is higher roughly by a factor of 2 and T(e0) roughly by 35% at a fixed P (tot)/n(e0) when compared to non-peaked profile cases. On a similar comparison, the neutron production rate is found to be higher roughly by a factor of 4. Here T(e0) and T(i0) are central electron and ion temperatures respectively, n(e0) is the central electron density and P(tot) is the total input power. The central confinement improves significantly whereas there is about 20% improvement in global electron kinetic-energy confinement. The ion heating is improved in the pellet case, partly due to a higher collisionality between the background ions and the energetic minority, but more significantly by a reduction of local ion-energy transport in the central region. Full ray-tracing calculations of power transferred to electrons and ions are consistent with the rate of rise of T(e0) and T(i0) in peaked- profile cases. The transport code simulation of these discharges reveals that there is a reduction of both X(e) and X(i) in the central region of the plasma in the ICRF heated peaked-profile discharges where X(e) and X(i) are the electron and ion heat conductivities respectively.

Additional information

Authors: BHATNAGAR V P, JET Joint Undertaking, Abingdon, Oxon. (GB);TARONI A, JET Joint Undertaking, Abingdon, Oxon. (GB);ELLIS J J, JET Joint Undertaking, Abingdon, Oxon. (GB);JACQUINOT J, JET Joint Undertaking, Abingdon, Oxon. (GB);START D F H, JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(89)38 EN (1989)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
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