An upgraded PCI diagnostic to detect and localize high-k waves and fluctuations in Alcator C-Mod*

Phase Contrast Imaging (PCI) diagnostic has been used previously to study mode conversion of ICRF waves$^{1}$ and plasma fluctuations in the ITG/TEM regime$^{2}$. Recent modifications to the imaging optics have increased the maximum k$_{R}$ from 8 cm$^{-1}$ to 25 cm$^{-1}$. New digitizers extend the frequency response to 5MHz (sampling rate of 10MHz). This makes it possible to study microscale turbulence in the ETG regime (k$_{\bot } \rho _{e}\sim $0.1, f$\le $5MHz). Furthermore, mode converted waves in the ICRF regime will be studied where k$_{\bot }\sim $10-25 cm$^{-1} $ correspond to ICW/IBW waves$^{1}$. A system consisting of a partially masked phase plate on a rotatable stage has been installed, which provides localized measurements for large k$_{\bot }$ fluctuations along the vertical 32 channel viewing chords$^{3}$. Initial results of high-k and vertical localization measurements will be presented. \\ \\$^{*}$Work supported by U. S. DOE under DE-FG02-94-ER54235 and DE-FC02-99-ER54512. \\ \\$^{1}$E. Nelson-Melby et al, Phys. Rev. Letts. \textbf{90}, 155004 (2003). \\$^{2}$N. Basse et al, Phys. Plasmas \textbf{12}, 052512 (2005). \\$^{3 }$S. Kado et al, Jpn. J. Appl. Phys. \textbf{34}, 6492 (1995).