Time-of-Flight Measurement of Photoneutron Energy Spectra

A technique has been developed for measuring photoneutron energy spectra which makes use of the time-offlight principle and a linear accelerator as a pulsed source of bremsstrahlung. Electrons from the linear accelerator impinge on a target at a repetition rate of which is controlled by the conduction time of an electron gun in the Van de Graaff injector. The interval of time is measured between the passage of the bremsstrahlung through a plastic scintillator near the ( gamma ,n) target and the detection of a neutron in another plastic scintillator located at the end of a seven-meter flight path, 120 deg to the path of the bremsstrahlung beam. The elapsed time spectrum is converted to a pulse-height spectrum which is analyzed into 256 channels. (A.C.)