A fission-fragment detector based on thin scintillating films has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing 4π detection of the fission fragments. The scintillation photons were registered with silicon photomultipliers. A measurement of the 235 U(n, f) reaction with this detector at DANCE revealed a correct time-of-flight spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described.

The 236 U(n, γ) reaction cross section has been measured for the incident neutron energy range from 10 eV to 800 keV using the DANCE γ-ray calorimeter at the Los Alamos Neutron Science Center. The cross section was determined with the ratio method, a novel technique using the 235 U(n, f ) reaction as a reference. The results of the experiment are reported in the resolved and unresolved resonance energy regions. Individual neutron resonance parameters were obtained below 1 keV incident energy using the R-Matrix code sammy. The cross section in the unresolved resonance region is determined with improved experimental uncertainty. It agrees with both ENDF/B-VII.1 and JEFF-3.2 nuclear data libraries. The results above 10 keV agree better with the JEFF-3.2 library.

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