Ion Cyclotron Resonance Heating (ICRH)

Electromagnetic waves with frequencies of the ion cyclotron motion around the magnetic field lines may be absorbed in the plasma, thereby heating the ions.

Electromagnetic waves with frequencies in the range of the ion-cyclotron motion (typically several ten MHz) can be absorbed in the plasma depending on the detailed geometry and launch conditions. The kinetic energy of the resonant ions increases and may reach even energies comparable to those of fast fusion alpha particles in later fusion reactors. The kinetic energy is transferred to the other plasma particles via collisions such that the plasma heats up.

For Wendelstein 7-X such an ICRH system is being prepared for the experimental campaign OP2.1 starting in 2022. It comprises an RF-generator with frequencies tunable between 25 to 38 MHz, a coaxial transmission line to the torus and an in-vessel strip antenna close to the plasma. A schematic plot of the components close to the torus is shown below. The particular task of this heating system is twofold: direct heating of ions in high-density plasmas, where conventional ECRH heating fails, and secondly the creation of fast ions which allow to study the optimized fast-particle confinement expected for the Wendelstein 7-X HELIAS configuration.

This ICRH system is currently being prepared in cooperation with the Ecole Royale Militaire in Brussel and the Research Center Jülich (FZJ). In parallel, the numerical modelling of ion heating in the complex 3D magnetic field geometry of Wendelstein 7-X is developed for later comparison of the experiments with theory.