Analytical and simulation feasibility study for an ion cyclotron resonance heating (ICRH) antenna for the TJ-II stellarator.

The TJ-II Stellarator is a machine with low magnetic shear with four periods, major and minor radii 1.5m, 0.22m, operating at B_T≈ 1T, with hydrogen plasmas in the density range n ≈ 0.3×10¹⁹- 5×10¹⁹m^-3 and electron temperatures T_e=900-300eV with corresponding T_i=80-150eV for low-density plasmas without NBI and high-density plasmas with hydrogen NBI. TJ-II is equipped with two gyrotrons (53.2GHz, 300kW each), used for plasma startup with ECRH electron heating and one NBI system of 1.2MW, aimed at ion heating and fast particle physics study. Recently, an ICRH system has been proposed to heat the ions more efficiently. To develop an ICRH system in TJ-II, an analytical study and a simulation have been undertaken to determine the best ion cyclotron range of frequencies and ICR heating scenario for the whole density range using experimentally obtained density and magnetic field profiles. Heating of single species plasmas with second harmonic ion heating and two species plasmas with minority and hybrid ion heating are considered. A two- and three-strap ICRH antenna design is under study and the simulations are carried out with COMSOL Multiphysics. The analytical and simulation results will be presented.