Presheath and double layer-like structures in the core of an argon helicon plasma source with uniform magnetic fields

Summary form only given. An argon helicon plasma source is operated at ~3 mTorr neutral pressure, 500 W RF power, and 900 G axial magnetic field strength generating plasma densities of ~10¹² cm^-3. A grounded plate is placed two antenna lengths down stream from the edge of the m = -1 helicon antenna. A double layer-like structure consisting of a localized axial electric field of approximately 8 V/cm over 1-2 cm is observed upstream from the grounded plate. The high potential side is shown to contain a population of relatively hot (Te ~ 10 eV) electrons. The magnitude of the potential step is shown to be enough to trap the hot electrons. The interaction between the double layer-like structure and the plate´s presheath is investigated.