Assessment of Plasma–Material Interaction During High-Power Helicon Operation in the DIII-D Tokamak Using STRIPE Framework

The DIII-D tokamak recently demonstrated high-power helicon wave operation, coupling ∼360 kW of RF power at 476 MHz into L-mode plasmas using a traveling-wave comb-line antenna. While effective for heating and current drive, helicon waves can induce strong RF sheath potentials that enhance plasma–material interactions (PMI) and drive localized erosion. We assess these effects using STRIPE[1], a multi-physics modeling suite integrating SOLPS, COMSOL, RustBCA, and GITRm. Edge plasma conditions are constrained by He-beam spectroscopy. Simulations of two DIII-D H-mode discharges (#196154 and #200882) with different antenna–plasma gaps predict minimal net carbon erosion, consistent with low impurity radiation. Parametric scans show erosion depends strongly on local plasma density and sheath potential, but only weakly on coupled power in the present regime. These results inform helicon-compatible operating scenarios that mitigate PMI.

This work is sponsored by US DOE under the contract DE-AC05-00OR22725 (ORNL); DE-FC02-04ER54698 (GA); DE-SC0024369 and DE-SC0021285 (RPI).