Nonlinear trapping simulations for helicon plasma sources

Summary form only given, as follows. The nonlinear trapping process is an important effect which may contribute to the extraordinary high wave damping rate of helicon sources. We are developing a numerical simulation method and code to study nonlinear phenomena in plasmas with complex wave structure. An open system with a steady-state initial distribution function is considered. In the case of low density (n<10/sup 11//cm/sup 3/) where collision effects can be neglected, the distribution function as a function of time and space is obtained by solving the motion equation and tracing particle trajectories back to the starting point. Our simulation results for a sinusoidal wave field show that trapped electrons with wave-particle phase confined within a range of phase less than 2/spl pi/ appear as the wave field intensity increases, and the distribution function shows bunching of fast particles around 40 eV at an E/sub z/ field intensity of 100 V/m. We are studying the effects of a wave number spectrum, a frequency spectrum, and field components including /spl mu//spl nabla//sub z/B/sub z/ and E/sub /spl perp// in addition to the electrostatic E/sub z/ on the nonlinear trapping process. The modelling of wave fields are based on the simulation results from our ANTENA II and MAXEB codes. We will also carry out the simulation utilizing MAGIC particle-in-cell code and comparison between these two approaches will be discussed. We will at the same time compare our simulation results with current experiments being carried out on our helicon experimental facility.