Precision Neutron Polarimetry

Proposed PANDA and abBA experiments aim to measure the correlation coefficients in the polarized neutron beta decay at the SNS. The goal of these experiments is 0.1{\%} measurement which will require neutron polarimetry at 0.1{\%} level. The FnPB neutron beam will be polarized either using a $^{3}$He spin filter or a supermirror polarizer and the neutron polarization will be measured using a $^{3}$He spin filter. Experiment to establish the accuracy to which neutron polarization can be determined using $^{3}$He spin fliters was performed at Los Alamos National Laboratory in Summer 2007 and the analysis is in progress. The details of the experiment and the results will be presented.