Ion-Current Downstream of a Carbon Dioxide Helicon Double Layer

Abstract

Energy-resolved ion measurements in a carbon dioxide helicon radio-frequency plasma containing an oblique current-free double layer are obtained using a retarding field energy analyzer for standard operating conditions (i.e., 0.4 mTorr, 250 W, and 140 G). Two ion populations corresponding to thermal ions and an energetic ion beam, respectively, are observed and spatially mapped downstream of the double layer, which is in the region of diverging field lines. The measurements are mirrored about the main reactor axis using cylindrical geometry, and a 3-D image is generated.