SOLPS-ITER drift modelling of ITER burning plasmas with narrow near-SOL heat flux channels

Abstract

SOLPS-ITER code simulations with fluid drifts activated are used to examine the consequences for divertor performance, under burning plasma conditions, of a reduction in scrape-off layer (SOL) cross-field transport such that the outboard midplane SOL parallel heat flux width, λq is reduced to the very low values predicted by the experimental scaling in [T. Eich et al., Nucl. Fusion 53 (2013) 093031] for high plasma current operation on ITER. The decrease of λq from the standard value (~3.5 mm) used in the ITER SOLPS modeling database, to λq ~ 1–2 mm expected from the scaling, leads to a strong narrowing of the operational window in terms of divertor heat loading limits. To maintain similar levels of sub-divertor neutral pressure, pn (one of the key divertor operational parameters) as those obtained with standard transport, higher levels of neon impurity seeding are required when transport is reduced, yielding higher Zeff at the upstream separatrix and requiring further integrated modelling to assess the impact on confinement. The simulations also demonstrate that the strong increase in in-out target peak power loading asymmetry at low pn seen for standard transport when drifts are switched on in the code is preserved, and in fact worsens, for low transport. This significantly reduces margins for power handling control at lower pn if heat flux channels will be narrow on ITER.

Keywords

• SOLPS-ITER
• ITER modeling
• Narrow SOL