Giant dipole resonance photofission and photoneutron reactions in U238 and Th232

New measurements of photofission and photoneutron reactions on ^238U and ^232Th in the giant dipole resonance (GDR) energy region were performed at the laser Compton-scattering -ray source of the NewSUBARU synchrotron radiation facility using a high-and-flat efficiency moderated ^3He detection array. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events was performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron reactions (, in) with i=1--3 and photofission reaction (, F) were discriminated by considering a Gaussian distribution of prompt-fission neutron (PFN) multiplicities predicted by the theory of evaporation in sequential neutron emission from excited fission fragments. We report experimental (, n), (, 2n), (, 3n), and (, F) cross sections, average energies of PFNs and of (, in) photoneutrons, as well as the mean number of PFNs per fission and the width of the PFN multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions. The new experimental results are compared with statistical-model calculations performed with the empire 3. 2 Malta and talys 1. 964 codes on the present data and with prompt fission emission calculations obtained with the Los Alamos model in the frame of the most probable fragmentation approach with and without sequential emission.