Abstract
A critical question for the use of ion cyclotron range of frequency (ICRF) heating in the ITER device and beyond is interaction of fast waves with energetic ion populations from neutral beam injection (NBI), fusion reactions, and minority ions accelerated by the RF waves themselves. Several experiments have demonstrated that the interaction between fast waves and fast ions can indeed be strong enough to significantly modify the NB ion population. To model the RF/fast ion interaction and the resulting fast ion distribution, a recent extension of the full wave solver TORIC v.5 that includes non-Maxwellian effects has been combined with the Monte Carlo NUBEAM code through an RF “kick” operator. In this work, we present an initial verification of the NUBEAM RF “kick” operator for high harmonic fast wave (HHFW) heating regime in NSTX plasma.
Highlights
Self-consistent modeling of the interactions between fast waves (FWs) and fast ions, introduced either from neutral beam injection (NBI) or from fusion-generated alpha particles, is important for both present-day experiments and for ITER
The version of TORIC implemented in TRANSP [14], which is able to solve the Maxwellian equations in the high harmonic frequency heating regimes [4], has been recently extended to include non-Maxwellian ion effects [5]
The structure of the differential form of the wave equation implemented in TORIC in the finite-Larmor-radius (FLR) approximation is maintained and 0th-order FLR coefficients of the wave equation are replaced by the corresponding elements of the full hot-plasma dielectric tensor in which the k⊥ value in the argument of the Bessel functions is obtained by solving the local dispersion relation for FWs only
Summary
Self-consistent modeling of the interactions between fast waves (FWs) and fast ions, introduced either from neutral beam injection (NBI) or from fusion-generated alpha particles, is important for both present-day experiments and for ITER. The fast-ion population changes the wave propagation and absorption, while the wave damping on fast-ions modifies their distribution. The latter implies that fast-wave heating could impact and perhaps give leverage over Alfvénic instabilities driven by beam ions. Specific to NSTX [1], FWs can modify the behavior of - and, under certain conditions, even suppress - fast ion driven instabilities such as toroidal Alfvén eigenmodes (TAEs), global Alfvén eigenmodes (GAEs) and fishbones [2, 3].
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