Super-X and conventional divertor configurations in MAST-U ohmic L-mode; a comparison facilitated by interpretative modelling

Moulton, David; Harrison, J. R.; Xiang, L.; Ryan, P. J.; Kirk, A.; Verhaegh, Kevin; Wijkamp, Tijs A.; Federici, Fabio; Clark, J. G.; Lipschultz, B.

doi:10.1088/1741-4326/ad4f9c

Super-X and conventional divertor configurations in MAST-U ohmic L-mode; a comparison facilitated by interpretative modelling

Journal Article · Tue Jun 11 00:00:00 EDT 2024 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ad4f9c· OSTI ID:2440993

Moulton, David ^[1]; ^[1]; ^[1]; Ryan, P. J. ^[1]; Kirk, A. ^[1]; ^[1]; ^[2]; ^[3]; Clark, J. G. ^[1]; ^[4]

UK Atomic Energy Authority (UKAEA), Culham (United Kingdom)
Dutch Institute for Fundamental Energy Research (DIFFER) (Netherlands); Eindhoven Univ. of Technology (Netherlands)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Univ. of York (United Kingdom)

Measurements are presented, alongside corresponding interpretative SOLPS-ITER simulations, of the first MAST-U experiments comparing ohmically heated L-mode fuelling scans in Conventional divertor (CD) and Super-X divertor (SXD) configurations. In experiment, at comparable outer mid-plane separatrix electron density, $$n_{e,\textrm{sep,OMP}}$$, the maximum lower outer target heat load was found to be a factor 16 $$\,\pm\,7$$ lower in SXD compared to CD. In simulation, a factor 26.8 reduction was found (slightly higher than the experimental range), suggesting an additional reduction in SXD compared to the factor 9.3 expected from geometric considerations alone. According to the simulations, this additional reduction in the SXD is due to a net radial transport of the energy remaining downstream of the $$T_e = 5$$ eV location. This energy is carried out of the critical (highest heat load) flux tube by deuterium atoms, demonstrating the importance of a longer legged divertor which provides space for this to occur. Importantly, in both simulation and experiment, the SXD has minimal impact on the upstream n_e and T_e profiles. Spectral inferences of detachment front movement in SXD compare well between simulation and experiment. In regions of high magnetic field gradient, the parallel movement of the front towards the X-point becomes less sensitive to increasing $$n_{e,\textrm{sep,OMP}}$$, in qualitative agreement with simplified models and previous predictive simulations. Additional aspects, regarding the target ion flux rollover, upstream separatrix temperature and drift effects, are also presented and discussed.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 2440993

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 7 Vol. 64; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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Super-X and conventional divertor configurations in MAST-U ohmic L-mode; a comparison facilitated by interpretative modelling

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