  Energy losses in a magnetic nozzle radiofrequency plasma thruster are
investigated to improve the thruster efficiency, which are calculated from
particle energy losses in fully kinetic simulations. The simulations calculate
particle energy fluxes with a vector resolution including the plasma energy
lost to the dielectric wall, the plasma beam energy, and the divergent plasma
energy in addition to collisional energy losses. As a result, distributions of
energy losses in the thruster and the ratios of the energy losses to the input
power are obtained. The simulation results show that the plasma energy lost to
the dielectric is dramatically suppressed by increasing the magnetic field
strength and the ion beam energy increases instead. In addition, the divergent
ion energy and collisional energy losses account for approximately 4-12% and
30-40%, respectively, regardless of the magnetic field strength.
