Seppo Sipilä

ASCOT simulations of electron energy distribution at the divertor targets in an ASDEX Upgrade H-mode discharge

Electron energy distribution at the divertor targets was calculated with the Monte Carlo code ASCOT for an ASDEX Upgrade H-mode discharge. The scrape-off layer (SOL) plasma background was obtained from the edge fluid code SOLPS. The orbit-following of test particles was performed assuming a fixed Maxwellian plasma background, accounting for the effects of the magnetic geometry, Coulomb interaction with the background and a prescribed electric potential. The energies recorded from the electrons impinging on the divertor targets indicated that, close to the plates, there should be strong deviations from the thermal Maxwell–Boltzmann distribution. In addition, details of the magnetic geometry and parallel plasma temperature and density profiles were observed to significantly impact the target energy distributions. The obtained discrepancy between the Monte Carlo and fluid results indicates a lack of self-consistency in fluid modelling due to kinetic effects in a medium-collisionality SOL.