  The photon arm of the Compton polarimeter in Hall A of Jefferson Lab has been
upgraded to allow for electron beam polarization measurements with better than
1% accuracy. The data acquisition system (DAQ) now includes an integrating
mode, which eliminates several systematic uncertainties inherent in the
original counting-DAQ setup. The photon calorimeter has been replaced with a
Ce-doped GSO crystal, which has a bright output and fast response, and works
well for measurements using the new integrating method at electron beam
energies from 1 to 6 GeV.
