The role of ion magnetization on plasma generation in a magnetic nozzle rf device

Abstract

Two dimensional mappings of the floating potential, Ar II emission and ion saturation currents are used to characterize an 80 cm long magnetized rf plasma column. The data brings new evidence supporting that the level of ion magnetization under the rf loop antenna plays an important role for the efficient generation of plasma over an extended region when the magnetic nozzle is sufficiently separated from the antenna. Densities up to 10^{18} m^{-3} and a blue core are observed for an rf power of 200 W and magnetic fields above 400 G when ions are magnetized. The local wall charging under the antenna is probed and observed to change coherently with the local ion magnetization and seems critical to the global creation and transport of energetic electrons, which are indirectly observed far from the antenna when the ion Larmor radius is much smaller than the glass tube radius over the entire region of investigation.