Investigating RF Far-Field Sheath Rectification on SPARC using the STIX Finite-Element Code

The upcoming SPARC device will be able to achieve > 20 MW of ion cyclotron radio frequency (ICRF) power to reach fusion relevant temperatures. Although the ICRF frequency range is a robust method of heating tokamaks, it is prone to adverse effects such as RF sheath rectification that damage plasma-facing components. New capabilities now allow to numerically model RF sheath rectification using a finite sheath impedance boundary condition (BC) developed by [J. Myra Phys. Plasmas 2015]. Using this sheath BC, far-field sheath behavior in the poloidal cross section of SPARC is investigated using the cold plasma RF finite-element code ``Stix’’ through a non-linear iteration. Using lower order thermal corrections to the cold plasma dielectric, Stix can emulate the resonance broadening and Landau damping within the core. This research will report on the dependence of various single pass absorption regimes and plasma parameters on the strength and locations of far-field rectification within SPARC.