Ball‐Pen Probe Measurements in L‐Mode and H‐Mode on ASDEX Upgrade

Abstract Experimental investigations of the plasma potential, poloidal electric field and electron temperature during L‐mode and ELMy H‐mode were performed on ASDEX Upgrade by means of a probe head containing four ball‐pen probes and four Langmuir probes. This allows to measure simultaneously the floating and plasma potential at the same time which are related by the electron temperature. Thus a combination of ball‐pen probes and Langmuir probes offers the possibility to determine the electron temperature directly with high temporal resolution. This novel temperature measurement method is compared to standard techniques. The influence of the electron temperature on the usual calculation of the poloidal electric field from the gradient of the floating potential is determined by a comparison to the poloidal electric field derived from the plasma potential (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)