Measurement of MeV-range total cross sections using reactor neutrons

A new method for the measurement of neutron total cross sections in the energy region 0.8 to 3.0 MeV is described. Use is made of the fast neutron flux of a pool-type reactor and the energy is defined by a time-of-flight spectrometer consisting of a scattering and a subsequent detecting fast organic scintillator. Considerable attention has been focussed upon experimental design with an aim to optimization of both the time resolution and the signal-to-noise ratio. The resolution obtained ranged from 15 keV at 0.8 MeV to 50 keV at 3.0 MeV. The statistical error associated with the cross section was 2% in the central energy region and rose to 10% at the extrema. Typical results are presented for 27Al.