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Funding Information: The author would like to thank Eric Meier of Zap Energy Inc. and Darren Stotler of Princeton Plasma Physics Laboratory for the private communication that has enabled this work. This work was performed by LLNL under Contract DE-AC52-07NA27344 and was also supported by the Fulbright Finland Foundation, the Walter Ahlstr?m Foundation, Svensk-?sterbottniska Samfundet, Svenska Tekniska Vetenskapsakademien i Finland, the Foundation for Aalto University Science and Technology, Waldemar von Frenckell's Foundation, and Academy of Finland grant agreement No 285143. Funding Information: This work was performed by LLNL under Contract DE-AC52-07NA27344 and was also supported by the Fulbright Finland Foundation, the Walter Ahlström Foundation, Svensk-Österbottniska Samfundet, Svenska Tekniska Vetenskapsakademien i Finland, the Foundation for Aalto University Science and Technology, Waldemar von Frenckell's Foundation, and Academy of Finland grant agreement No 285143. Publisher Copyright: © 2021 The Authors Copyright: Copyright 2021 Elsevier B.V., All rights reserved. A fluid collisional-radiative model for H2 has been implemented in the edge-fluid code UEDGE and compared to the kinetic neutral code EIRENE on a simple, 2D, orthogonal domain with a constant, static plasma distribution. The novel CRUMPET Python tool was used to implement dissociation and energy rate coefficients that consider molecular-assisted processes, binding energy, and radiation due to molecular processes into the UEDGE fluid molecular model. The agreement between the fluid and kinetic molecular models was found to be within 20% when corresponding rates were used in UEDGE and EIRENE for a domain with absorbing boundaries. When wall recycling was considered, EIRENE predicted up to a factor of 2.2 higher molecular densities than UEDGE at T < 5 eV. The difference is due to the absence of radial gradients driving diffusive wall fluxes and, thus, recycling in UEDGE and molecular self-scattering in EIRENE, and is likely dependent on plasma profiles and domain geometry. Comparison of the molecular energy sources in EIRENE and UEDGE suggest the constant elastic scattering rate coefficient used in UEDGE needs to be updated to a temperature-dependent coefficient and that atom-molecule equipartition should be considered in the EIRENE model for background plasma density in excess of 1×1019m-3. Finally, collisional-radiative CRUMPET simulations indicate that the vibrational molecular populations become comparable to the ground-state molecular population when the plasma temperature decrease below 6 eV and, thus, require time-dependent evaluation.

In this contribution a benchmark of the 2D edge codes TECXY and EDGE2D-EIRENE is presented. A conventional DEMO scenario is considered by assuming a simplified geometry, with the target plates perpendicular to the separatrix, and a pure Deuterium plasma. Despite the different models adopted in the two codes, mainly related to the description of the neutral dynamics and to the different boundary conditions, the results show a good match both in terms of power load profiles on the outer target and predicted trends for global quantities. A scan in density and in diffusion coefficients is performed in order to identify the characteristic conditions and the different regimes of the SOL. Comparable values and similar dependency of the global quantities as a function of the power decay length is also observed. Keywords: EDGE2D, EIRENE, TECXY, DEMO, Divertor

Change of H α intensity profiles depending on magnetic configurations is observed in the divertor plasma. It can be explained by the magnetic field line structures in the ergodic layer and the divertor legs. The behavior of neutral particles in the plasma periphery is investigated by a three-dimensional neutral particle transport simulation code which assumes that the distribution of the plasma flow onto the divertor plates corresponds to that of the strike points calculated by magnetic field line traces. Vertical H α intensity profiles and polarization resolved H α spectra are calculated by the simulation code including the effect of Doppler broadening, fine structure splitting and polarization of the H α emission, which agree well with the measurements in various magnetic configurations. It shows spontaneous formation of high neutral density in inboard side of the torus, which is independent of the magnetic configurations in LHD.