Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

Multi-megawatt Ion Cyclotron Range of Frequencies (ICU) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RI') antenna electric near-field E8 that is rectitied in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the 1CIU antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRIF antenna configurations, used for experiments M 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the Eh. fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.