JET-P(91)53

Synergistic Effects Between Lower Hybrid and Fast Magnetosonic Waves in JET

Combined Lower Hybrid Current Drive and Ion Cyclotron Resonance Heating experiments have been carried out in JET, starting in 1990 with the prototype LH system. Non-inductive currents up to 1.5MA have been produced in ICRF heated plasmas with volume averaged electron temperature of 2.2keV. The main "signature" of synergy is the large increase in the photon temperature of the hard X-ray emission, representative of the fast electron distribution, which has been observed during combined LH plus ICRH heating. Deposition profiles of direct electron heating have been obtained by means of LH power modulation experiments. In presence of ICRH, they exhibit an enhanced power transfer in the plasma core which cannot be accounted for by the launched LH power alone. A possible explanation is the electron damping of the fast wave on fast electron tail via Transit Time Magnetic Pumping leading to the observed heating and current drive efficiency.
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JETP91053 1.00 Mb