Drift effects in SOLPS-ITER simulations of the COMPASS tokamak SOL

The final experimental campaign of the COMPASS tokamak encompassed a series of L-mode and H-mode discharges, incorporating both normal and reversed directions of the toroidal magnetic field and plasma current. This presents an excellent opportunity to investigate the influence of charged particle drifts within the scrape-off layer (SOL) region.

Our study is motivated by observations of the divertor plasma profiles, mainly the electron temperature and heat flux. The profiles are often deformed when compared with theory and fluid simulations without drift terms. A possible manifestation of cross-field drift-driven transport in SOL was reported during the operation of COMPASS by UKAEA. Interestingly, a recent statistical study of divertor heat flux profiles in H-mode plasma did not indicate any correlation between B-field orientation and near-SOL decay lengths, leaving other aspects to be explored.

In this contribution, we present the first results of fluid simulations utilizing the SOLPS-ITER code applied to the COMPASS SOL incorporating effects of particle drifts. We use the High-Resolution Thomson Scattering system (HRTS), an infrared camera, and an array of divertor probes to constrain the simulation parameter space and obtain a reasonable agreement with the experiment. A comparison of simulations with and without drift effects together with the results from reversed B-field experiments yields insight into the divertor plasma profiles deformations.