Multi-diagnostic probe head for near-wall electric and magnetic measurements in medium-size tokamaks

We present a fully developed, small-size multi-diagnostic probe head for the characterization of near-wall (scrape-off layer and divertor region) electric and magnetic plasma properties in Medium-Size Tokamaks (MST). The probe head can be mounted on a number of reciprocating probe manipulators of MST devices. It contains one high electron emissive probe (EEP) [1, 2], two cold Langmuir probes (CLP), two retarding field analyzers (RFA) and two miniaturized 3-axial magnetic pick-up coils (MPC) for magnetic field fluctuations measurements. The EEP and the two CLP are placed on almost the same radial position (shadowing effects considered) making various Langmuir probe measurement techniques (e.g. fast electron temperature measurements) applicable. The CLPs can further simply be replaced by two pins, geometrically parallel to the magnetic field, capable of determining the electron energy distribution function (EEDF) in the plasma [3]. Combining these measurements with the ion energy distribution function (IEDF) of the plasma, gained from the RFAs, the real local heat flux can be determined [4]. Here we present preliminary measurement results obtained in the linear magnetic device located at the Jozef Stefan Institute, Slovenia. Soon the probe head will be integrated into the Tokamak a Configuration Variable (TCV) for first scrape-off layer measurements.