Seed plasma generated by employing helicon source in rotating magnetic field driven field reversed configuration

The performance of seed plasma produced by helicon source using half-helical antenna in rotating magnetic field (RMF) driven field reversed configuration (FRC) may has significant impact on the RMF-FRC formation, maintenance and disruption processes. Under typical helicon plasma discharge conditions, i.e., FR wave frequency ω/2π=4 MHz, axial static magnetic field B₀ =100 G, gas pressure p_Ar=100 mTorr, RF input power P_in=2.5 kW, analytical results of a three-dimensional (3-D) numerical model show that the two core plasma parameters, plasma density and temperature, exhibit completely different time evolution processes, the electron density peak gradually moves inward from the discharge tube edge region and reaches the center region after hundreds of RF cycles, approximately about 0.1 ms; meanwhile, the electron temperature peak is initially located within a large radial range of the discharge tube, then gradually moves closer to the two circular arm ends of the antenna, and finally located in a thin layer of the discharge tube edge region, the entire process takes about 100 RF cycles, or 0.025 ms, to reach a steady state. Understanding the formation process of the seed plasma is critical for optimizing the overall performance of RMF-FRC.