Electron Beam Polarimetry for the CREX Experiment

The CREX experiment in Hall A at Jefferson Lab recently measured the neutron radius of Ca-48. This was accomplished via measurement of the parity violating (PV) scattering asymmetry which is mainly sensitive to the neutron distribution. The measured asymmetry scales linearly with the beam polarization which is typically a key systematic error for PV experiments like CREX. The beam polarization was provided by a combination of Compton and Møller polarimeters. I will show the final results from the two polarimeters for CREX and discuss key insights and improvements. I will also talk about issues that came to light that will need to be addressed for the next generation of parity experiments.