Determination of window thickness for efficient microwave injection into ECR plasma

An Electron Cyclotron Resonance (ECR) source can deliver stable high intensity positively charged ion current. It is a magnetically confined plasma produced by injection of microwave power. Efficient coupling of microwave power into the plasma is achieved by using suitable window that provides better impedance matching between the launching device and the plasma load. The thickness and dielectric property of the window is of utmost importance for effective microwave injection. The main objective of the present study is to find out a suitable window for a particular operating frequency. High Frequency Structural Simulator (HFSS) code has been used to analyze the wave propagation in 1.69-12 GHz frequency range. This enables us to find the optimum thickness of the dielectric window that would give maximum power absorption in singly ionized Argon and Nitrogen plasma for a specific range of injected microwave frequencies.