Takahashi, KazunoriCharles, ChristineBoswell, RodHatakeyama, Rikizo2015-12-062015-12-061070-664Xhttp://hdl.handle.net/1885/17030Electron energy probability functions (EEPFs) are measured across the radius (0 ≤ r < 6.85 cm) of a low pressure (0.3 mTorr) helicon plasma source terminated by a current-free double layer. The source field of about 130 G is generated using a Helmholtz coil pair and the radio frequency (rt) power is maintained at 250 W. All EEPFs exhibit a distribution with a temperature Te bulk out to a break energy ebreak and a relatively depleted distribution for higher energies with a lower temperature Te tail· Te bulk and Te tail are about 8 eV and 5 eV, respectively, for r<4 cm and increase up to about 14 eV and 9 eV near the source wall, i.e., near the rf antenna. ebreak is found to correspond to the potential drop of the double layer for the central part of the source and to the sheath potential near the wall.4 pages© 2008 American Institute of Physics Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Physics of Plasmas and may be found at http://doi.org/10.1063/1.2959137 http://publishing.aip.org/authors/copyright-reuse http://www.sherpa.ac.uk/romeo/issn/1070-664X Author can archive publisher's version/PDF (Sherpa/Romeo as of 7/12/2015).Electron energy probability functions (EEPFs)radius (0 ≤ r < 6.85 cm)helicon plasmalow pressure (0.3 mTorr)Helmholtz coilradio frequency (rt)200810.1063/1.29591372015-12-08