The role of plasma-atom and molecule interactions on power \& particle balance during detachment on the MAST Upgrade Super-X divertor

• DOI: 10.48550/arxiv.2304.09109
• Publication Date: 2023-01-01
• Authors: K. Verhaegh; B. Lipschultz; J. Harrison; F. Federici; D. Moulton; N. Lonigro; Stijn Kobussen; M. O’Mullane; Nicholas J. Osborne; P. Ryan; T. Wijkamp; B. Kool; E. Rose; C. Theiler; A. Thornton
• Keywords: Super-X Divertor; Plasma Detachment; Mast Upgrade; FOS: Physical sciences; plasma detachment; QC770-798; 530; Physics - Plasma Physics; Plasma Spectroscopy; Plasma Physics (physics.plasm-ph); Nuclear and particle physics. Atomic energy. Radioactivity; Plasma-Molecular Interactions; MAST Upgrade; Atomic physics. Constitution and properties of matter; plasma-molecular interactions; Super-X divertor; plasma spectroscopy

This paper shows first quantitative analysis of the detachment processes in MAST Upgrade Super-X divertor (SXD). We identify an unprecedented impact plasma-molecular interactions involving molecular ions (likely $D_2^+$), resulting strong ion sinks (Molecular Activated Recombination - MAR), leading to a reduction target flux. The MAR exceed sources before electron-ion recombination (EIR) starts occur, suggesting that significant ionisation occurs outside chamber. In EIR region, $T_e \ll 0.2$ eV is observed and remains these deep detached phases. total sink strength demonstrates capability for particle (ion) exhaust Configuration. Molecular Dissociation (MAD) dominant volumetric neutral atom creation process can lead electron cooling 20\% $P_{SOL}$. measured radiative power losses \emph{in chamber} are consistent with inferred hydrogenic losses. suggests intrinsic impurity radiation, despite carbon walls, minor contrasts previous TCV results, which may be associated enhanced plasma-neutral reduced chemical erosion detached, tightly baffled SXD. above observations have also been higher heat flux (narrower SOL width) type I ELMy H-mode discharges. provides evidence characterisation this general.