3.2 Measurement of capture croos section of Dy and Hf in the energy region from 0.003 eV to 10 eV

摘要

Applying a detector assemly of Bi_4Ge_3O_(12) (BGO) scientillators (each size: 5X5 cm~2, 7.5 cm thick) to prompt capture gamma-rays measruement as a total energy absorption detector, the absolute measurement of capture cross sections of nat-Hf and nat-Dy ahas been made in the energy region from 0.003 eV to 10 eV by the linac time-of-flight (TOF) method using a 12.7 m station. Incident thermal neutron flux was absolutely determined by using the BGO detection system with a Sm sample. to extend the neutron flux mesurement from the thermal netutron region to higher netron energies, the ~(10)B(n, a #gamma#) reaction was applied. Absolute capture yield for the dample was obtained by the saturated caputre yield at a large resonance of the dampe. The inside of the through-hole in trhe BGO detection system is covered with ~6LiF tiles of 3 mm in thickness, which are useful to shield neutrons scattered by the sample below 100 eV. The effects by the scattered neutrons at higher energies have been investigated using a graphite sampel.