Measurement of neutron capture cross sections for Dy and Hf between 0.001 and 10 eV using total energy absorption detector

Applying a detector assembly of Bi4Ge3O12 (BGO) scintillators (each size: 5x5 cm2, 7.5 cm thick) to prompt capture γ-rays measurement as a total energy absorption detector, the absolute measurement of capture cross sections for Hf-nat and Dy-nat has been made in the energy region from 0.001 to 10 eV using the linac time-of-flight method. Incident thermal neutron flux was absolutely determined by using the BGO detection system with a Sm sample. To extend the neutron flux measurement from the thermal neutron region to higher neutron energies, the 10B(n,αγ) reaction was applied. Absolute capture yield for the relevant capture sample was obtained by the saturated capture yield at a large resonance of the sample. The through hole to set the sample in the BGO detection system is covered with 6LiF tiles of 3 mm in thickness, which are useful to shield lower energy neutrons below 100 eV. We have also investigated the BGO sensitivity to scattered neutrons with a graphite sample instead of the Dy or Hf sample. The results of the Dy and the Hf capture cross sections showed good agreement with the previous measurements and the evaluated data in ENDF/B-VI and JENDL-3.2