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The question of ICRF power deposition profiles in JET is experimentally addressed by means of a square wave modulated RF perturbation. The study is conducted in D(H) and D(He3) plasmas for two heating scenarios. In D(He3) plasmas and for central heating in a scenario where mode conversion into a Bernstein wave is accessible, the direct power deposition profile on electrons is derived. This accounts for 15% of the total coupled power and extends over 25% of the minor radius. Outside the RF power deposition zone, observation of the diffusive electronic transport enables an estimate of Xe inside the inversion radius surface. In non monster-sawtooth discharges and for low central temperature gradient the obtained value is small, typically a tenfold lower than estimations of X(e) deduced by heat pulse propagation on similar discharges at radii larger than the inversion radius. In D(H) and for the minority heating scheme, a large fraction of the ICRF modulated power is absorbed by the minority ions and modulation of the minority tail is observed with a characteristic i-e slowing down time. In this scheme, electron heating occurs only through collisions with the minority ion tail and the modulation of the electron temperature is unobservable in sawtoothing discharges. This is interpreted as a consequence of the long i-e equipartition time, acting as an integrator for the modulated ICRF signal. Finally, a correlation between the time of the sawtooth crash and the periodic turn off of the ICRF power is deduced and its consequence for modulation experiment is reviewed.

Additional information

Authors: GAMBIER D J ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(88)52 EN (1988)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
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