Turbulence Measurements with the Upgraded Phase Contrast Imaging Diagnostic in Alcator C-Mod

The Phase Contrast Imaging diagnostic (PCI) in Alcator C-Mod has been upgraded to improve the frequency and wavenumber sensitivity and provide localized measurements along the beam. Optional optics configurations are available for optimizing turbulence measurements in different wavenumber ranges. With the low-k setup (6 cm$^{-1})$ and the widened beam, new features of the Quasi-Coherent (QC) modes were observed. The coherence of the QC modes is reduced toward the X-point. Furthermore, the spatial location of the coherence reduction moves with the X-point. With the medium-k setup (12 cm$^{-1})$, three coupled (f$_{3}\sim $f$_{2}$+f$_{1}$ and k$_{R3}\sim $k$_{R2}$+k$_{R1})$ semi-coherent modes have been detected. The initial analysis of these two measurements will be presented. For the high-k setup (up to 40 cm$^{-1})$, initial tests with sound burst transducers have shown capability to measure modes with wavenumbers up to 40 cm$^{-1}$. Currently, the PCI is operating with the high-k setup to search for the short wavelength turbulence in the ETG range and results will be presented as available.