47th EPS Conference on Physics P5.1028

SOLPS-ITER simulations of the COMPASS

K. Hromasová1,2, D. Coster3, M. Komm1, J. Seidl1, D. Tskhakaya1

1 Institute of Plasma Physics, Czech Academy of Sciences, Prague, 2 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague, Czech Republic 3 Max Planck Institute for Plasma Physics, Garching, Germany

The tokamak transport code SOLPS-ITER [1] is an invaluable tool in assessing the edge plasma physics. Its complex treatment of neutrals by the Monte Carlo code EIRENE allows it to accurately capture plasma recycling and neutral transport. [2] This facilitates minute investiga- tions of momentum and power losses in the SOL, ranging from the simple SOL to detachment. Herein, SOLPS-ITER is used to gauge the edge transport regime in the COMPASS tokamak. The COMPASS tokamak [3] is a compact machine operated at IPP Prague, Czech Repub- lic. Its extensive edge diagnostics coverage [4] invites interpretative SOLPS-ITER modelling, facilitating experiment-code comparison both upstream ( diagnostic, recip- rocating probes) and downstream ( probe arrays and infrared thermography). It is thought that typically the COMPASS edge plasma operates in the sheath-limited regime, where parallel gradients are small and the carbon divertor target is exposed to plasma of rel- atively high temperatures. Multiple factors contribute to this, including its short connection length to the outer target (5 − 10 m). In this contribution, we present the first SOLPS-ITER simulation of tokamak COMPASS produced exclusively by its team. It is a deuterium, drift- free plasma with kinetic neutrals, based on the divertor L-mode discharge #17588, and it is representative of the typical COMPASS plasma. We carefully compare the modelling results to diagnostic measurements and discuss the choice of input parameters and boundary conditions. Analysis by two-point model formatting (2PMF) [5] reveals that the momentum and energy losses are very small throughout the SOL (< 20%), which corresponds to the sheath-limited regime. This might have implications for the employment of COMPASS in multi-machine scal- ings where the edge transport regime may be an important variable, such as [6].

References [1] S. Wiesen et al, Journal of Nuclear Materials 463 (2015) 480-484 [2] R. A. Pitts et al, Nuclear Materials and Energy 20 (2019) 100696 [3] R. Pánek et al, Plasma Physics and Controlled Fusion 58 (2015) 014015 [4] V. Weinzettl et al, Journal of Instrumentation 12 (2017) C12015 [5] P. C. Stangeby, Plasma Physics and Controlled Fusion 60 (2018) 044022 [6] J. Horácekˇ et al, 60 (2020) 066016