Progress and present status of the investigation of the fission fragment angular anisotropy in the slow neutron induced fission of ~235 U

摘要

The progress and present status of the experimental and theoretical investigation of the fission fragment angular anisotropy in the slow neutron induced fission of a 235 U aligned target are presented. the upgraded experimentalequipment has allowed us to gain more than a double increase of the accumulated statistics during the last two years. An improved data processing algorithm is developed. The obtained data are analyzed together with the total neutron, total fission and spinseparated fission cross sections in the neutron energy interval 0-20 eV in order to obtain a new set of s-wave resonance parameters. The data are analyzed on the basis of a new theoretical description of fission process accounting for the interference between s-wave neutron resonances with different spins. Two fitting procedures were used, supplementary to each other. They are equivalent in the formalism of the description fo cross sections. but different in the minimization algorithms. Three fission channels are taken into account for the spin group J = 3 (K= 0.1,2) and two for the spin group J= 4 (K=1,2). The obtaiend set of resonance parameters and K-channel contributions for the slow neutron induced fission of ~235 U are discussed.