Electromagnetic Modelling of Dielectric loads in front of an ICRH ITER array using TOPICA and HFSS codes for comparison

The antenna scattering (S‐matrix) or impedance matrix at location where the antenna is connected to the power system is of crucial importance to assess compliance with power handling requirements and to design the tuning‐and‐matching system. The electrical behaviour of an Ion Cyclotron Resonance Heating (ICRH) ITER antenna in front of an infinite isotropic load was assessed numerically using the HFSSR and TOPICA codes for comparison. The calculations were performed at 45 MHz, for various thicknesses of the vacuum layer, various relative permittivities ε′ for dielectric medium without losses (ε″  =  0), ε′ ranging from 81 to 1000 and for various conductive losses ε″  =  σ/ε0⋅ω, for electrolyte medium (ε′  =  81), ε″ ranging from 0 to 1000. The numerical results obtained with TOPICA and HFSS codes show a good overall agreement in case of vacuum, dielectric and electrolyte mediums. The best absorption of the fast magneto‐sonic (Alfven) waves into the loads (i.e. the minimum of the module of antenna input reflection coefficient S11) is obtained around ε′  =  400 for dielectric medium and around ε″  =  400 for electrolyte case.