Effect of ICRF Mode Conversion at the Ion-Ion Hybrid Resonance on Plasma Confinement in JET

The objective of the present study is to find out the range of the IIHR layer radial position within which the plasma confinement in conventional L-mode regime may be improved. The recent ICRF-MC heating experiments on JET (RF power dominated D(3He)-discharges, PRF/(Ptot-PRF) 2.0) were analyzed. The RF power coupled into plasma in the ICRF-MC scenario improved confinement properties of discharges with respect to the (OH+NBI)-phase at the central locations of IIHR (|rii/apl| < 0.3) with the best result (up to ~60% improved confinement) closer to axis and at dipole antenna phasing. A shift of IIHR towards the plasma edge (|rii/apl| > 0.4) resulted in degradation of confinement. An analysis of plasma confinement based on plasma diamagnetic and thermal energy content, and results of modeling of the absorbed power at ICRF-MC are discussed.
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