Retiring risk for ion cyclotron range of frequency heating in SPARC through modeling

The SPARC tokamak will primarily rely on ion cyclotron range of frequency (ICRF) heating to reach the high temperatures necessary for fusion breakeven. This talk will cover modeling activities at MIT and CFS leading to the final design of the SPARC Ion Cyclotron Antenna (ICAN). Installing a pair of 4 strap toridally aligned antennas into each of 7 ports should allow for >25 MW coupled power. Two-dimensional modeling efforts of far-field sheath rectification during ICRF heating is underway using the STIX code developed at MIT. The results from scans for various absorption scenarios will be reported, including implications for high-Z impurity generation. Modifications to the TORIC code allow for multiple antennas at specified poloidal locations corresponding to the SPARC ICAN geometry. Simulations show that RF waves from antennas located above and below the plasma mid-plane damp somewhat off-axis (rho ~ 0.2-0.3) as compared with a single antenna at the mid-plane (rho ~ 0-0.1) due to intersection of the launched waves with the cyclotron resonance layer at finite vertical displacement from the mid-plane.