EFDA-JET-CP(01)02/38

Peripheral Plasma Perturbations and Transient Improved Confinement in JET Optimized Shear Discharges

Peripheral plasma cooling is known to induce a transient state of improved core energy confinement detected in the form of a transient core electron temperature (Te) rise. The effect has been observed in many tokamaks [1-5] in both Ohmic and auxiliarily heated plasmas at sufficiently low density. In JET, earlier peripheral plasma cooling experiments had been performed at a density too high for the effect to be observed. This paper presents the first attempts to perform such experiments in JET in Optimised Shear conditions, where the low density and high heating power are favourable to the occurrence of the effect. Ultimately the aim for these experiments would be to look for a synergy between peripheral cooling and formation of a persistent Internal Transport Barrier (ITB), in order to exploit the peripheral cooling as a triggering tool for the ITB formation.
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