Speaker
Description
Faithful simulations of the tokamak edge plasma, particularly in view of detachment access, are crucial for the design of future fusion reactors. The COMPASS Upgrade tokamak, currently under construction at IPP CAS, Prague, will feature reactor-relevant magnetic fields and target energy fluxes. [1] Previously, predictive SOLPS-ITER [2] simulations have been presented of two COMPASS-U H-mode scenarios, ITER-like #24300 and high-performance #5400. [3,4] Performed using the "structured grid" SOLPS-ITER version, these simulations suffered the drawback that protruding divertor baffles prohibited the construction of a sufficiently wide SOL grid. As a result, a large fraction of the input power (27 % and 47 %, respectively) was deposited on the outer boundary of the computational region, effectively escaping the simulation. It was suspected that this missing power may be responsible for the observed partial detachment, which occurred in spite of the lack of impurity seeding.
In this contribution, we present new simulations of these H-mode scenarios, performed using the SOLPS Wide Grids version [5], where the plasma domain covers the entire edge plasma up to the first wall. Power balance assessment and loss factor calculation show that the new solutions differ significantly from those achieved with the older code version. The plasmas are attached with high peak heat loads (increased from 12 MW/m2 to 25 MW/m2 on the outer target of scenario #24300) and low pressure losses. This is in line with sheath-limited conditions achieve at similar separatrix parameters on Alcator C-Mod, the closest tokamak relative of COMPASS Upgrade. [6] Power injected into the simulation region is recuperated entirely as incident on the divertor targets or the first wall in the form of plasma heat, neutral heat or radiation. Our results underscore the possible positive impact in switching to the Wide Grids SOLPS-ITER version and the importance of impurity seeding for target heat load mitigation in COMPASS Upgrade H-modes.
[1] P. Vondracek et al, Fusion Engineering and Design 169 (2021) 112490
[2] S. Wiesen et al, Journal of Nuclear Materials 463 (2015) 480-484
[3] I. Borodkina et al, SOLPS-ITER predictions for power and particle exhaust in COMPASS Upgrade tokamak, poster contribution to the 26th International Conference on Plasma Surface Interactions in Controlled Fusion Devices, 2024, Marseille, France
[4] M. Komm et al, Nuclear Fusion 64 (2024) 076028
[5] W. Dekeyser et al, Nuclear Materials and Energy 27 (2021) 100999
[6] B. Lipschultz et al, Fusion Science and Technology 51 (2017) 369-389