Slow wave measurement using the WVU 300 GHz collective scattering diagnostic

Recent experiments in helicon plasma sources by Kr\"{a}mer \textit{et al}. [2006] and Kwak \textit{et al}. [2006] have employed mm-wave technology to investigate electron densities in a pulsed source and density fluctuations due to ion-acoustic waves, respectively. Measurement of the temporal and spatially resolved electron densities by Kramer was accomplished with a mm-wave interferometer. The ion-acoustic waves measured by Kwak employed a collective scattering system with a heterodyne detection scheme. The WVU 300 GHz quasi-optical collective scattering diagnostic, uses a homodyne detection method similar to the interferometer, designed to measure the ``slow'' wave. Experimental parameters observed to heat ions in the plasma edge in conjunction with theoretically calculated wave numbers associated with the slow wave, as seen in Kline \textit{et al}. [2002], were examined for evidence of the slow wave using the mm-scattering diagnostic. Here we present initial wave number spectrum measurements of the slow wave in a helicon plasma source. M. Kr\"{a}mer, B. Clarenbach, and W. Kaiser, Plasma Sources Sci. Technol. \textbf{15}, 332 (2006). J.G. Kwak, S.J. Wang, S.K. Kim, and S. Cho, Phys. Plasmas \textbf{13}, 074503 (2006). J.L. Kline, E.E. Scime, R.F. Boivin, A.M. Keesee, and X. Sun, Plasma Sources Sci. Technol. \textbf{11}, 413 (2002).