Description
Heat and particle exhaust in the scrape-off layer represent one of the most critical challenges for tokamak operation. The MAST-Upgrade (MAST-U) tokamak has been specifically designed to address this issue through the implementation of the Super-X divertor. The Super-X combines strong magnetic flux expansion, enhanced baffling, and extended connection lengths to maximise power dissipation and reduce peak target loads.
In this work, we use the SOLEDGE3X-EIRENE simulation code to model plasma transport in MAST-U and to assess the performance of the Super-X divertor in comparison with more conventional configurations, such as the standard and elongated divertor, in order to quantify the benefits of the Super-X divertor for heat and particle exhaust.
SOLEDGE3X combines fluid plasma modelling and Monte Carlo tracking of neutral particles (via EIRENE), incorporating key physics such as transverse and parallel transport, plasma-neutral interaction, radiation and drift.
The presented study aims to explore and characterise the benefit of the Super-X divertor configurations in MAST-U. The work takes advantage of a newly implemented mesh generator in SOLEDGE3X, which enables the modelling of the complex magnetic configurations of MAST-U. This capability is exploited to investigate plasma behaviour in three MAST-U divertor magnetic configurations, namely the Conventional, Elongated and Super-X configurations, characterised by different values of total flux expansion and leg length. All analysed discharges are L-mode unseeded plasmas, NBI-heated (1.5-1.7 MW) with comparable plasma current ($I_P∼750$ kA), magnetic field ($B_T$ = 0.55T), $P_{SOL}$=1.2 MW and similar core density and temperature. Simulation results are compared with experimental diagnostics, including Thomson scattering, Langmuir probes, and bolometry.