Pressure balance between midplane and inner and outer divertor in ASDEX Upgrade H-mode discharges

Abstract

Electron pressure profiles have been obtained in the outer midplane and along the divertor target using various diagnostics in ASDEX Upgrade. Inter-ELM and ELM phases of H-mode discharges with different power- and neutral fluxes in the divertor are investigated. To check the parallel pressure balance, mapping using equilibrium reconstruction is corrected/checked by physics constraints, like the upstream separatrix temperature according to power balance. Good agreement between the midplane pressure and the divertor pressure obtained from Langmuir probe measurements, assuming a Mach flow = 1 into the sheath, is observed for the outer scrape-off layer (SOL). A pressure reduction around the strike point by more than one order of magnitude is observed for low power, high neutral flux conditions. Strong detachment/pressure loss is seen in the inner divertor for all conditions. During ELMs, higher electron pressures are obtained in the outer divertor SOL compared to the midplane.