High precision measurement of the polarization in a large target

The individual error sources of the proton polarization measurement during the SMC ʹ93 run were carefully analyzed. Main error groups were the calibration temperature, the NMR signals in thermal equilibrium and those of the enhanced polarization, and the LF gain ratio. After corrections to the raw polarization values, the overall error amounts to ΔPP = 2.1%. The averaging of the polarization values, the correlations between the errors and the polarization homogeneity throughout the large target were also considered, resulting in a final relative accuracy of 3%.