Important progress was made on cross section measurement of neutron induced nuclear reaction by Dr. Guohui Zhang’s group, in the State Key Laboratory of Nuclear Physics and Technology, Physics School of Peking University. Their research paper “¹⁴⁹Sm(n,α)¹⁴⁶Nd Cross Sections in the MeV Region” is published in recent Physical Review Letters ( PRL 107, 252502 (2011) ). The journal referee remarked that “the work of Zhang et al contributes significantly to the field and may also serve to guide future experiments”. This work was performed jointly with scientists from the Joint Institute of Nuclear Research, Dubna, Russia, National University of Mongolia, University of Lodz, and Oak Ridge National Laboratory.

The¹⁴⁹Sm(n,α)¹⁴⁶Nd cross section is of interest for nuclear physics, astrophysics as well as nuclear energy applications. However, in the MeV region where the energy dependence of cross section is changing fairly rapidly, there is no measurement datum. As a result, evaluated nuclear data libraries rely mainly on nuclear model calculations in this region, and hence there are large differences between the various evaluations.

Measurements are performed at the 4.5 MV Van de Graaff accelerator of Peking University. By using double-section gridded ionization chamber as alpha detector and with large-area samples, 149Sm(n,α)146Nd cross sections are measured at five energy points. Measurement at 6.0 MeV is repeated with thicker samples, and the consistency is achieved. Small cross section as 50 μb is obtained. Model calculations are also performed, and a good agreement is achieved between measurements and calculations from thermal to MeV energies.

Cooperating with Dubna for more than ten years and basing on the 4.5 MV Van de Graaff accelerator of Peking University, Zhang’s group has carried out measurements and calculations of cross sections for a series of (n,α) reactions of light, medium and heavy nuclei. Most of their experimental results have been collected in the EXFOR data library of IAEA (there are 20 reactions and 46 datasets up to now).