Developments on and Plans for IShTAR
Résumé
IShTAR (Ion Sheath Test ARrangement) is a linear magnetic facility developed by and operated at the Max-Planck-Institut für Plasmaphysik (IPP) in Garching in cooperation with several universities and institutes. It is equipped with a helicon plasma source and an ICRF (Ion Cyclotron Resonant Frequency) single strap antenna. It is used to investigate the interactions between the launched wave and a plasma that is representative (plasma density, temperature and wave propagation) for a tokamak edge.Whereas the device was originally meant to develop the tools to measure the electric field produced by the ICRF wave inside the sheath on the antenna limiters in order to provide data to check and benchmark the RF sheath models, it can actually provide major contributions in many other areas related to plasma production and RF-plasma interactions. Just to name a few:
- helicon physics: the helicon has one of the largest diameter in the world and will soon be equipped with a major power upgrade (up to 750 kW generator power between 3.9 MHz and 26.1 MHz);
- refinement of RF fields measurement methods: by comparing the modelling of the electromagnetic field distribution (including eigenmodes and superposition of the fields of helicon and RF antenna) inside the vessel with the measurements;
- RF plasma production and modelling: the device was used to test plasma production for RF wall cleaning, and to investigate for which conditions the plasma is initiated inside the antenna box. It is essential to avoid such phenomenon in high power ICRF system on tokamak, but IShTAR provides the liberty for detailed investigations of the conditions under which these to-be-avoided phenomena occur.
IShTAR is further designed as an experimental platform dedicated to international co-operations: to improve remote access for participants, it is equipped with an intranet to manage the operations and the documentation. The processing system has sharable notebooks and remote access to the discharge database is possible.