DIVIMP-B2-EIRENE modelling of ¹³C migration and deposition in ASDEX Upgrade L-mode plasmas

Carbon transport and migration were studied experimentally and numerically in a high-density, low-confinement mode plasma in the ASDEX Upgrade tokamak. On the last day of plasma operation of the 2004–2005 experimental campaign, ¹³CH₄ was injected into the vacuum vessel from the low field side midplane. A poloidal set of tiles was subsequently removed and analysed for ¹³C deposition. In this work the measured deposition profile is interpreted using the impurity transport code DIVIMP. The simulated poloidal distribution of ¹³C deviates significantly from the measured profile. The simulations indicate that ¹³C is promptly deposited at the wall in the vicinity of the injection port, and is transported to the low field side divertor plate predominately via the scrape-off layer. The B2-EIRENE plasma solution produce stagnant plasma flow in the main scrape-off layer, in contrast to measurements in ASDEX Upgrade and other tokamaks. This is the likely cause of the discrepancy between the measured and the calculated poloidal distribution of the ¹³C deposition. Key model parameters of DIVIMP were varied to determine their effect on the simulated deposition profile.