Upgrade of reflectometry profile and fluctuation measurements in Alcator C-Mod

This article reports on the upgrade of the reflectometry profile and fluctu ation measurements in Alcator C-Mod. The reflectometer consists of five amp litude modulated O-mode millimeter-wave channels operating between 50 and 1 10 GHz. The system provides the electron density profile for densities up t o 1.5 X 10(20) m(-3). An upgrade has been implemented to improve the reliab ility of the system, eliminate 2 pi ambiguities in the group delay measurem ent, and enhance the fluctuation measurements. An upgrade of the 88 GHz cha nnel has been installed, which allows fluctuations on both the upper and lo wer sideband signals to be measured independently with high resolution. Som e preliminary fluctuation and density profile results are discussed. (C) 19 99 American Institute of Physics. [S0034-6748(99)76101-0].