Optimised polarisation measurements on Bragg peaks

Experimentally the asymmetry A (or the flipping ratio R) is deduced from the two count rates observed for |+〉 and |-〉 neutron spin states. Since the count rates for the two spin states may be quite different and both require to be corrected for background, the optimum strategy for the measurement is important. We present here the theory for optimisation of the accuracy of measurement of A (or R) within the constraint of a fixed total measuring time.