Jefferson Lab HRS Optimization Measurement for the PRex-II Experiment

The RMS radius of the neutron distribution in a heavy nucleus $R_N$ provides an important test of nuclear theory. Furthermore $R_N$ is used in the determination of the density dependence of symmetry energy of neutron rich matter; this dependence is an important input in neutron star structure, heavy iron collision and atomic parity violation experiment calculations. The PRex-II experiment was performed from June to September 2019 to measure $R_N$ for the $^{208}$Pb nucleus using the parity violating weak neutral interaction. This experiment was done in Jefferson lab experimental hall A using the High Resolution Spectrometer (HRS) pair. This talk with present the preliminary results from HRS Optics calibration measurements for the PREX-II and will discuss the implication of these calibration results on the systematic error in $R_N$.