The standard branching ratio 10B(n, α0) to 10B(n, α1)

The 10B(n, α) standard cross sections have received considerable attention in recent years due to their relatively poor database available at higher incident neutron energies (above 100 keV) and the problems they caused in the ENDF/B-VI standards evaluation process. In view of a forthcoming new evaluation of the standard cross sections and the demand from the standards sub-group of the WPEC, IRMM has conducted a new measurement of the branching ratio.A Frisch gridded ionization chamber has been used as detector to measure the α-particles from the reaction. The advantage of this set-up is the nearly full coverage of the 2π angular cone. The 10B-samples (~30 μg/cm2) have been prepared by our sample preparation group. Our GELINA white spectrum neutron source has been used to deliver the neutrons in the energy region from eV to 1 MeV.The preliminary data analysis seems at a first glance to be in better agreement with the ENDF/B-VI evaluation than with the most recent measurement of the branching ratio by West...