Application of new techniques to ORELA neutron-transmission measurements and their uncertainty analysis: the case of natural nickel from 2 keV to 20 MeV

The neutron transmission through a 2.54-cm sample of natural nickel has been measured for neutron energies between 2 keV and 20 MeV. Known background sources are described, and the methods used to correct for these backgrounds are presented. An in-depth uncertainty analysis is given for this measurement, with explicit formulas derived for each effect contributing to the cross-section uncertainty. Parameters uncertainties and correlations among the parameters describing the backgrounds, deadtime, and other sources of uncertainty are given. To obtain a covariance matrix for this measurement, the final cross-section results are binned into 15 energy groups, and covariance matrix is provided for this 15-group set. We find that the largest contributions to the cross-section uncertainty are due to sample properties, beam monitors (used to normalize sample-in and sample-out counts), and ORELA power variations during the run which affect the deadtime correction. Overall uncertainties in the cross section for this measurement are on the order of 2%. The resulting cross sections are compared with the ENDF/B-V file for nickel; many resonances not presently in the file are observed, and energy-scale differences are noted