The effect of different wave launch positions on ion cyclotron resonance heating in stellarator

The magnetic field configuration of the CN-H1 stellarator exhibits non-axisymmetric characteristics, which significantly affect the propagation and absorption of electromagnetic waves. Therefore, the wave launch position plays a crucial role in determining the effect of ion cyclotron resonance heating (ICRH). This paper utilizes the three-dimensional full-wave code to simulate ICRH with different wave launch positions on CN-H1. Employing the 4He (H) minority ion heating scheme, it explores the impacts of the wave launch position [poloidal position, toroidal position as well as low-field side (LFS) and high-field side (HFS)] on ICRH. Our study suggests that the wave launch position in the toroidal direction should aim to maximize the length of the ion cyclotron resonance layer (ICRL) at the magnetic axis directly opposite the ion cyclotron range of frequency antenna. In the poloidal direction, the wave launch position should be placed as close as possible to the ICRL at the target heating position. Ion absorption in the target region requires the fulfillment of multiple conditions, and electron absorption exhibited favorable absorption characteristics across several simulated wave launch positions, particularly at the toroidal 0° position, where excellent core electron absorption was observed. Due to reduced collisional damping, better wave penetration, and more favorable wave accessibility on the LFS under current device conditions, the heating effect on the LFS is superior to that on the HFS.