Photofiss;.on of uranium by high energy bremsstrahlung

Radiochemical measurements have been made of fission yield at 3 GeV and forward-backward ratios at 5 GeV in the photofission of natural uranium by bremsstrahlung. The targets used for recoil studies consisted of a natural uranium foil of thickness 100 mgcm-2 (2.5x1020U nuclei cm-2) sandwiched between aluminium foils which acted as catchers for fission product recoils. The target used for yield measurement of fission products consisted of uranyl acetate powder. Aluminium foils (10 mg cm-2) were used to monitor the bremsstrahlung beam. The yield results are analysed in terms of a two component mass yield curve, consisting of a low energy asymmetric component and a high energy symmetric component. The relative weights of these components were calculated from cross section data as 30% low energy and 70% high energy, but a better fit was obtained with a much smaller contribution (27%) from the high energy component. A possible explanation is discussed briefly. (T.I.)