Speaker
Description
Standalone EIRENE simulations of neutral deuterium emission across the DIII-D low-field side (LFS) divertor target accurately predict the measured Lyman and Balmer series radiative emission in both attached and detached divertor conditions when constrained by the measured 2D Divertor Thomson Scattering (DTS) electron temperature (Te) and (ne), and Langmuir probe (LP) ion current density. A rigorous description of the spatial distribution and absolute densities of hydrogenic neutrals, and validation of plasma radiation predicted by scrape-off layer (SOL) codes is critical for the design of future fusion devices. Hence, for the measured ion flux to the divertor target and the plasma conditions, and disregarding edge-localized modes and other transients, the combination of the plasma recycling and neutral transport models in the neutral Monte-Carlo code EIRENE, and published atomic and molecular rates tabulated in the AMJUEL data repository, reproduces the measured neutral deuterium emission within the uncertainty of the measurements and simulation setup. These studies separate the validation of neutral particle transport, and atomic and molecular physics, from significantly more uncertain plasma transport in plasma-neutral coupled SOL codes, such as EDGE2D-EIRENE and SOLPS-ITER.
In detached conditions, inclusion of photon opacity of Lyman-alpha and Lyman-beta line emission in the EIRENE simulation further improved the agreement with the measured Lyman-alpha and Balmer-alpha emission well within the uncertainties of the measurements. In contrast, EIRENE executed on plasmas predicted by EDGE2D-EIRENE overpredict Lyman-alpha emission by up to a factor of 8, and underpredict the Balmer-alpha and the Balmer-gamma emission by factors of 2 and 10, respectively. Furthermore, EDGE2D-EIRENE predicts an order of magnitude lower molecular and atomic densities compared to EIRENE when constrained by DTS and LP measurements, implying that the momentum losses due to plasma-neutral collisions are significantly underpredicted in EDGE2D-EIRENE.
SOLPS-ITER simulations of DIII-D low and high-confinement plasmas, including cross-field drifts and Lyman line emission photon opacity are presented to assess the impact of photon opacity on the predicted 2D plasma distribution, and Lyman and Balmer emission intensity in the LFS divertor. To assess the fidelity of the updated neutral gas and radiation models in SOLPS-ITER, the predicted 2D poloidal profiles of ne and Te are compared to the measured profiles.
*See the author list of C.T. Holcomb et al., Nuclear Fusion 64 (2024) 112003.