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IShTAR is a linear magnetized plasma test facility dedicated to the investigation of RF wave/plasma interaction. The IShTAR ICRF system consists of a single strap RF antenna. When using the antenna for plasma production without an external plasma source, it is shown that the plasma is either produced in front of the antenna strap or inside the antenna box depending on the antenna parameters. Here, we present experimental and numerical investigation of the plasma initiation parametric dependencies. Detailed pressure and RF power scans were performed in helium at f = 5.22MHz and f = 42.06 MHz. The experiment shows the parameter ranges for which the plasma is produced in front of the strap, or inside the antenna box. These ranges are validated by simulations with the RF dinity model, and by theoretical predictions. [ABSTRACT FROM AUTHOR]

The recent scientific research on ASDEX Upgrade (AUG) has greatly advanced solutions to two issues of Radio Frequency (RF) heating in the Ion Cyclotron Range of Frequencies (ICRF): (a) the coupling of ICRF power to the plasma is significantly improved by density tailoring with local gas puffing; (b) the release of RF-specific impurities is significantly reduced by minimizing the RF near field with 3-strap antennas. This paper summarizes the applied methods and reviews the associated achievements. [ABSTRACT FROM AUTHOR]