Neutron Transmission Cross Sections in the Kilovolt Region

Neutron transmission cross sections have been measured with about 2 kev resolution in the energy range from 2 kev to 25 kev, and to higher energies in some case. The neutrons, produced by the ${\mathrm{Li}}^7\mathrm{}(p,n)\mathrm{}{\mathrm{Be}}^7$ reaction with a van de Graaff generator, were detected by a highly efficient (∼15 percent) bank of boron trifluoride filled proportional counters placed to detect neutrons emitted at an angle of 120° from the proton beam direction. Measurements at the lower energies were made possible by a collimator and shield around the counters, which reduced background, and by the high efficiency obtained by many counters embedded in an array in a paraffin moderator. Resonances were observed in Na, Ti, V, Mn, Fe, Co, and Ni.