Advanced probe for transport measurements in medium-size tokamaks

The characterization of outward filamentary plasma transport in Medium-Size Tokamaks (MST) is an important objective of current fusion plasma research. We aim at improving the diagnostic of transport events in the Scrape-Off Layer (SOL) and further inside by means of various types of newly developed electrical probes combined with the associated probe measurement procedures. Presently, a New Probe Head (NPH) for measurements in the SOL of MSTs is under development. This probe head will be mounted on the reciprocating probe manipulators of MSTs. One important goal of the NPH is to introduce electron emissive probe (EEP) measurements into MSTs. If this task is successful, it is planned to construct further probe heads for tokamaks and stellarators, equipped with several EEPs along with additional diagnostics. The NPH, being the main topic of this presentation, will be equipped for measuring several plasma parameters simultaneously, like electron and ion temperature (Te and Ti), cold floating potential, Vfl, and plasma potential, Vpl, as well as the ion density ni in different ways so that a comparison of various measurement techniques will be possible. Local magnetic fluctuations will also be measured by means of miniaturized pick-up coils mounted inside the probe head. On a m s timescale, it will also be possible to compare the fluctuations of the floating potentials of two cold Langmuir probes with the EEP's floating potential, which is expected to be close to or at the plasma potential. The results of the probe measurements are supposed to complement the other plasma diagnostic methods in MSTs delivering more information on filamentary plasma transport. The poster describes first results of an EEP prototype in a test plasma chamber and discusses possibilities of the NPH and why these measurements are important and interesting.