Sequential modelling of ICRF wave near RF fields and asymptotic RF sheaths description for AUG ICRF antennas

Abstract

Abstract. A sequence of simulations is performed with RAPLICASOL and SSWICH to compare two AUG ICRF antennas. RAPLICASOL outputs have been used as input to SSWICH-SW for the AUG ICRF antennas. Using parallel electric field maps and the scattering matrix produced by RAPLICASOL, SSWICH-SW, reduced to its asymptotic part, is able to produce a 2D radial/poloidal map of the DC plasma potential accounting for the antenna input settings (total power, power balance, phasing). Two models of antennas are compared: 2-strap antenna vs 3-strap antenna. The 2D DC potential structures are correlated to structures of the parallel electric field map for different phasing and power balance. The overall DC plasma potential on the 3-strap antenna is lower due to better global RF currents compensation. Spatial proximity between regions of high RF electric field and regions where high DC plasma potentials are observed is an important factor for sheath rectification.

Recent progress on improving ICRF coupling and reducing RF-specific impurities in ASDEX Upgrade

“…Theoretical approaches [24][25][26] to model sheaths are being developed and will be validated against measurements on ASDEX Upgrade [11,27] and on IShTAR [28,29]. Theoretical insight of experimental results will provide key guidelines to design antennas with reduced sheaths and RF-induced impurities.…”

ICRF coupling in ASDEX upgrade magnetically perturbed 3D plasmas

“…Furthermore, we can test how large the deviation is between the experimental results and the numerical predictions. We will use for the simulations the COMSOL based RAPLICASOL code [43][44][45]. RAPLICA-SOL is able to handle the realistic geometry of ICRF antennas, and perform full-wave simulations on a finite element mesh.…”

Antenna to Core: A New Approach to RF Modelling

“…The Vorpal code [8,9], this publication] is an exception that uses a finite difference mesh to model the complex antenna geometry and includes cold plasma wave propagation from the antenna into a partial region of the core plasma. Other recently developed codes also focus on the cold plasma wave propagation near the antenna with perfectly matched layers (PML) at the domain boundaries such as RAPLICASOL [21,22]. Such outgoing boundary conditions as PML or absorbing boundary layers preclude the study of possibly important physics effects such as the reflection of waves back towards the antenna, far field sheath effects [23,24], and the modelling of scrape-off layer (SOL) propagation and collisional dissipation of coupled wave energy.…”