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

A hot (T-e approximate to 10 eV) electron population is observed in the core of a 3 mTorr argon helicon plasma source at 500W RF power and 900 G uniform axial magnetic field strength, 12 cm from the edge of the 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 adjacent to the hot electron population. The potential step generated by the electric field is shown to be large enough to trap the hot electrons. To our knowledge this is the first observation of these structures in the core of a helicon discharge. (C) 2014 AIP Publishing LLC.