The effect of electron cyclotron resonance heating on breakdown for start-up of a tokamak

Summary form only given. Although various experiments have been conducted routinely in many tokamak devices, the detailed physics background of so-called, start-up including processes of the plasma breakdown, burn-through, and current ramp-up has not been identified because too many parameters are involved together non-linearly and diagnostic tools are restricted in this phase. Plasma breakdown using electron cyclotron resonance heating (ECRH) has been proposed in the Korean superconducting tokamak advanced research (KSTAR) device because the loop voltage is limited due to thick vacuum liners and engineering limits of superconducting poloidal field coils. Particle-in-cell (PIC) simulation is a very effective tool to research the plasma phenomena but difficult to be applied to three dimensional, whole-size tokamak devices because of its large computation time. We developed a three-dimensional PIC code for investigating the breakdown of the tokamak start-up with ECRH. A simplified toroidal geometry is adopted for easy calculations with a prescribed magnetic field profile calculated for the KSTAR device. This PIC code includes Monte Carlo collision (MCC) routine for hydrogen atoms. In this work, we investigated the discharge characteristics and the effect of ECRH when the breakdown occurs in a tokamak. The influence of the magnitude of the toroidal magnetic field, loop voltage, gas pressure, and incident angle and intensity of ECRH is studied for breakdown in a tokamak.