First results with 3-strap ICRF antennas in ASDEX Upgrade. (5th July 2016) - Bobkov, V.
Abstract: The 3-strap antennas in ASDEX Upgrade allow ICRF operation with low tungsten (W) content in the confined plasma with W-coated antenna limiters. With the 3-strap antenna configuration, the local W impurity source at the antenna is drastically reduced and the core W concentration is similar to that of the boron coated 2-strap antenna at a given ICRF power. Operation of the 3-strap antennas with the power ratio between the central and the outer straps of 1.5 : 1 and 2 : 1 is adopted to minimize the ICRF-specific W release.