Local Electron Cyclotron Resonance in a Very High Frequency Neutral Loop Discharge

Abstract

Summary form only given. Neutral loop discharge (NLD) is variety of magnetic enhanced inductive coupled plasma (ICP). The NLD plasma source is characterized by a high-density plasma (>1011 cm-3) at low gas pressure (~103 Torr). Distinctive feature of NLD is magnetic field configuration with neutral loop (NL) that consists of continuous sequence of null magnetic field points connected in circle. The NLD is more efficiency at low gas pressure in comparison with ICP due to existence of new type collisionless electron heating - stochastic heating around the NL. The goal of this work is numerical simulation of the NLD plasma around the NL in order to determine effect of local electron cyclotron resonance (ECR) on electron heating in the very high frequency regime, when the electron collision frequency much less then driving frequency. Recently, existence of ECR in a weakly magnetized if inductive discharge has been evidenced. It was shown that electron temperature is at maximum near ECR condition. In addition, results of our numerical simulation show that the efficiency of the NLD is defined one more type collisionless electron heating - local ECR. The NLD can turn to regime in which maximum in radial distribution of electron temperature corresponds to the ECR condition at the radio frequency. Simulation shown that regime of local ECR heating is realized at low gas pressure and neglible Coulomb collisions. Efficiency of local ECR is enhanced with decreasing pressure (collision frequency) or increasing driving frequency. We used a fully electromagnetic code KARAT based on the particle-in-cell Monte-Carlo collision (PIC-MCC) method. The results of numerical experiment are in good agreement with the available experimental data.