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

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. (C) 2009 Elsevier B.V. All rights reserved.