Simulating energetic ions and enhanced neutron rates from ion-cyclotron resonance heating with a new fast, self-consistent full-wave / Fokker-Planck model*

Ion-cyclotron resonance heating (ICRH) is a key plasma actuator in experiments such as the JET, EAST, and WEST tokamaks, and use of ICRH is planned in the burning plasma experiments on SPARC and ITER. Previous experiments on Alcator C-Mod (P.T. Bonoli, Fusion Sci. Tech. 2007) and recent results from the JET DTE2 campaign (P. Jacquet, Conf. RF Power in Plasmas 2022) have demonstrated that ICRH generated fast-ions are important to understanding enhanced neutron rates and MHD instabilities.

Reproducing fast-ion effects in simulations is difficult. It requires self-consistent coupling of a full-wave solver and a Fokker Planck code which evolve multiple simultaneously resonant ion species. We introduce a new self-consistent model that iterates the TORIC or AORSA full-wave solvers with the CQL3D Fokker-Planck solver using the integrated plasma simulator (IPS). This model iteratively evolves the bounce-averaged ion distribution functions in both parallel and perpendicular velocity-space with a quasilinear RF diffusion operator (Lee, Phys. Plasmas 2017) valid in the ion finite Larmor radius (FLR) limit and the RF electric fields with the resultant non-Maxwellian FLR dielectric tensor (N. Bertelli, Nucl. Fusion 2017). This model provides non-Maxwellian ICRH simulations that are, fully self-consistent, fast, and interoperable with integrated modeling frameworks such as TRANSP/GACODE/IPS-FASTRAN. We demonstrate our model’s capabilities by performing simulations of Alcator C-Mod experiments where enhanced neutron rates resultant from fast-ions driven by harmonic damping of ICRH on deuterium were present in D(H) minority heating experiments, and we perform the first RF heating simulations of SPARC and ITER using self-consistent non-Maxwellian ion distributions to investigate the potential to enhance fusion gain using ICRF-generated fast ions.