Photofission Fragment Characteristics Of U-234,U-238 And Th-232 In The Barrier Region

The bremstrahlung induced fission of U-234,U-238 and Th-232 has been studied at the superconducting Darmstadt linear accelerator (S-DALINAC) in the excitation energy region close to the fission barrier. In this contribution results on the fission fragment mass, total kinetic energy ( TKE) and angular distributions will be presented. Fission fragment mass and TKE distributions from U-234 were studied for the first time in this energy region. The results have been analyzed in terms of fission modes and a dominant yield of the mass asymmetric standard-2 mode was found in all studied nuclei. No strong dependence of the fission mode weights on the excitation energy of the compound nucleus were found. Correlations between mass, TKE and angular distributions have been investigated in U-234 and Th-232. A correlation in form of an increased anisotropy for far-asymmetric masses and low TKE were found in both fissioning systems. A possible interpretation of this correlation in terms of fission modes is discussed. (C) 2014 The Authors. Published by Elsevier B.V.