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Abstract

Fission fragment energies and the emission angles with respect to the incident neutron beam were measured for 235-U(n,f) using a twin ionization chamber. A neutron energy range from thermal to 6 MeV in steps of 0.5 MeV was covered. The pre-neutron emission mass distributions were evaluated and described by a five- Gaussian representation. The parametrization made visible a sudden change in the incident neutron energy dependence for all but the symmetric fission parameters between 1.5 and 2.0 MeV, which might be due to pair breaking. From the total kinetic energy as function of mass split the sum of the deformations of the two fragments was evaluated in the frame of Wilkins static scission point model. Here clear proton pairing effects became visible which seem to make the even proton fragments less deformed than neighbouring odd proton fragments. The present data show also that the observed drop in TKE averaged over all fragments above 4 MeV is due to changes in TKE for different mass splits with excitation energy. At a yield level of 10**-6 cold fragmentation was observed for light fragment masses 87 to 110. In this mass region the light fragments are prolate and have a ground state electric quadrupole moment larger than approximately equal 1 barn. Angular distributions for the different fragment masses showed no mass dependence.

Additional information

Authors: STRAEDE CH, JRC GEEL ESTAB. (BELGIUM);BUDTZ JOERGENSEN C, JRC GEEL ESTAB. (BELGIUM);KNITTER H H JRC GEEL ESTAB. (BELGIUM), JRC GEEL ESTAB. (BELGIUM)
Bibliographic Reference: SEMINAR ON FISSION, HABAY-LA-NEUVE (BELGIUM), MAY 22- 23, 1986 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32780 ORA
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