Synergetic heating of D-NBI ions in the vicinity of the mode conversion layer in H-D plasmas in JET with the ITER like wall.

Abstract

Abstract. This paper discusses the extension of the 'three-ion' species ICRF technique for heating mixture plasmas using fast injected NBI ions as resonant 'third' species. In this scenario the ICRF power is absorbed by the fast beam ions in the vicinity of the mode conversion layer where the left-hand polarized RF electric field E + is strongly enhanced. The ions in the beam velocity distribution that have a Doppler-shifted resonance close to the mode conversion layer efficiently absorb RF power and undergo acceleration. We show first experimental observations of ICRF heating of D-NBI ions in H-D plasmas in JET with the ITER-like wall. In agreement with theoretical predictions and numerical modelling, acceleration of the D-NBI ions in this D-(D NBI )-H scenario is confirmed by several fast-ion measurements. An extension of the heating scheme discussed here is acceleration of T-NBI and D-NBI ions in D-T plasmas, offering the potential to further boost the Q-value in future D-T campaigns in JET.

Identification of an Optimized Heating and Fast Ion Generation Scheme for the Wendelstein 7-X Stellarator

“…The inverted Doppler-shifted minority species synergetic ICRF-NBI scenario experiments reported in Ref. [11] are a particular case of the scheme proposed in this Letter. In contrast to Ref.…”

“…In contrast to Ref. [11], the synergetic ICRF-NBI heating scheme proposed here does not limit the heating scheme to an inverted scenario, which refers to when the charge-to-mass ratio of the majority species is larger than the minority species. For large minority ion concentrations in inverted scenarios, parasitic electron rf-power absorption tends to dominate [18].…”

“…We show that this Doppler-shifted resonance minority species 4 HeðHÞ synergetic ICRF heating of hydrogen NBI ions in the optimized high mirror W7-X plasma equilibrium helps to improve energetic NBI ion confinement and further accelerate the injected beam ions. ICRF theory and simulations of JET experiments [11] using the SCENIC code [12] illustrate why the application of the Doppler-shifted resonance minority species ICRF-NBI heating scenario can be expected to be beneficial for the W7-X device. Validation of the SCENIC code against JET experimental data establishes important parametrization of the code, and establishes confidence in the promising predictions for W7-X.…”

“…Experimental and modeling efforts into synergetic ICRF-NBI heating in tokamaks, similar to the schemes developed in this Letter for the W7-X stellarator, can be found in Refs. [11,[13][14][15][16][17]. In particular, JET experiments in Ref.…”

“…The inverted scenario described in Ref. [11] avoids this problem by adjusting the rf-antenna frequency so that the energetic NBI ions absorb the rf power instead of the electrons, making it more sensitive to variations in ω a and the concentration of thermalized NBI ions. The scheme is referred to as a threeion species scheme in Ref.…”