Asymptotic analysis of the whistler waves propagation in space plasma thrusters

We present a three-dimensional Ray-Tracing solver, called RAYWh (RAY-tracing Whistler), for the electromagnetic propagation and power deposition in plasma sources for space thrusters, where high density plasmas (ranging from 1017 to 1019 particles/m3) are confined by general magnetic configurations with magnitude below < 0.15T. The 3D Maxwell-Vlasov equations are solved by means of a WKB asymptotic expansion, to investigate the propagation and absorption of whistler waves (excitation frequency is 13.56 MHz) under the influence of general confinement magnetic field, and axisymmetric realistic density profiles. The reduced set of the WKB equations for the wave phase and for the square amplitude of the electric field are solved numerically by means of Hamming's modified predictor-corrector method; the verification of WKB hypothesis are monitored during the simulation. The Ray Tracing approach is employed - for the first time - in the analysis of plasma sources for space plasma thrusters. A direct comparison between common helicon sources with axial, constant and uniform confinement magnetic field, and plasma sources with actual confinement magnetic field lines revealed a propagative picture with unconventional mode conversions, cut-offs and resonances inside the source that affect the power deposition.