Giant dipole resonance photofission and photoneutron reactions in U and Th

UおよびThにおける巨大双極子共鳴光核分裂と光中性子反応

Filipescu, D.*; Gheorghe, I.*; Goriely, S.*; 西尾 勝久   ; 宇都宮 弘章*; 洲嵜 ふみ  ; 廣瀬 健太郎  ; 他10名*

Filipescu, D.*; Gheorghe, I.*; Goriely, S.*; Nishio, Katsuhisa; Utsunomiya, Hiroaki*; Suzaki, Fumi; Hirose, Kentaro; 10 of others*

New measurements of photofission and photoneutron reactions on U and Th in the Giant Dipole Resonance (GDR) energy region have been performed at the laser Compton-scattering -ray source of the NewSUBARU synchrotron radiation facility. The photoneutron () with = 1-3 and photofission () reactions have been 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 (), (), () and () cross sections, average energies of PFNs and of(, ) photoneutrons, as well as the mean number of PFNs per fission and the width of the PFNs multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions.