Investigation of (n,??) Reaction for Rare-earth Elements in the MeV Neutron Energy Region

Cross sections and forward/backward ratios in the laboratory reference system were measured for {sup 143}Nd(n, {alpha}){sup 140}Ce at 4.0, 5.0, and 6.0 MeV, {sup 147}Sm(n, {alpha}){sup 144}Nd at 5.0 and 6.0 MeV, and {sup 149}Sm(n, {alpha}){sup 146}Nd at 6.0 MeV. A twin gridded ionization chamber and large-area back-to-back {sup 143}Nd{sub 2}O{sub 3} and {sup 147,149}Sm{sub 2}O{sub 3} samples were employed. Experiments were performed at the 4.5 MV Van de Graaff of Peking University, China. Fast neutrons were produced through the D(d, n){sup 3}He reaction by using a deuterium gas target. A small {sup 238}U fission chamber was employed for absolute neutron flux determination and a BF{sub 3} long counter was used as neutron flux monitor. Present experimental data are compared with previous measurements, evaluations, and model calculations.