Fission cross section measurement of Am-243 in the resonance neutron region using lead slowing-down spectrometer

Making use of a lead slowing-down spectrometer coupled to a 46 MeV electron linear accelerator, the fission cross section for Am-243 has been measured from 0.1 eV up to 10 keV relative to that for the 235U(n, f) reaction appeared in ENDF/B-VI. The pure Am-243 sample 20 mm in diameter was electrodeposited on a stainless steel plate (28 mm in diameter and 0.2 mm thick) and was placed together with the U-235 layer in the back-to-back type fission chambers. Number of atoms for the Am and U samples was determined by alpha and gamma spectrometries. The fission chambers were placed in the experimental hole covered with bismuth layers of 10 to 15 cm thick to suppress high energy capture gamma-rays from lead. For the measured cross section of the 243Am(n, f) reaction, the influence of Pu-239 produced by alpha-decay from Am-243 after the chemical purification has been corrected, and the result has been compared with the evaluated data in ENDF/B-VI and the JENDL-3.2 libraries, whose data were broadened by the energy resolution (40 % full width at half maximum) of the spectrometer. The JENDL-3.2 data below 30 eV are in good agreement with the present measurement within the uncertainties, but they are lower by a factor of about 1.5 above 30 eV. The ENDF/B-VI data are generally close to the present data except that the evaluation is lower by a factor of 2.5 in the energy range 15 to 60 eV. (author)