Cross calibration of the JLab, Hall C, Compton and M\o ller polarimeters and a study of systematic uncertainties of the Compton electron detector*

A Compton polarimeter was commissioned at Jefferson Lab, Hall C, for continuous non-invasive measurement of the electron beam polarization. It uses $\sim 1.5~kW$ of green light for the $\vec{e}-\vec{\gamma}$ scattering. The polarimeter has several planes of diamond micro-strip detectors to detect the Compton scattered electrons and a $PbWO_{4}$ crystal for detecting back-scattered photons. It was successfully used to measure the electron beam polarization along with periodic polarization measurements by the standard Moller polarimeter. The diamond micro-strip electron detector provided a standalone measurement of the beam polarization with $< 1\%$ statistical uncertainty per hour, for a 1.16 GeV, $180~\mu$A electron beam. The systematic uncertainties are projected to be better than 1\%. We will discuss the various contributions to the systematic uncertainties for the electron detector. We also collected data at low current for a Moller-Compton cross calibration. The preliminary results from the analysis of these data will be presented.