Search

We have developed a new setup to measure prompt γ -rays from the 235U(nth, f) reaction. The setup consists of two multi-wire proportional counters (MWPCs) to detect the fission fragments, two LaBr3(Ce) scintillators to measure the γ -rays. The highly efficient setup was installed at the PF1B beam line of the Institut Laue Langevin (ILL). We have successfully measured the γ -ray spectrum up to about 20MeV for the fist time in neutron-induced fission. [ABSTRACT FROM AUTHOR]

Multi-nucleon transfer channels of the reactions of 18O+232Th, 18O+238U, 18O+248Cm were used to measure fission-fragment mass distribution for various nuclides and their excitation energy dependence. Predominantly asymmetric fission is observed at low excitation energies for all the studied cases, with an increase of the symmetric fission towards high excitation energies. Experimental data are compared with predictions of the fluctuation-dissipation model, where effects of multi-chance fission (neutron evaporation prior to fission) was introduced. It was shown that a reliable understanding of the observed fission fragment mass distributions can be obtained only invoking multi-chance fissions. [ABSTRACT FROM AUTHOR]

It is shown that the multi-nucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multi-nucleon transfer channels of the reactions of 18O+232Th, 18O+238U and 18O+248Cm are used to study fission for various nuclei from many excited states. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model. Role of multi-chance fission in fission fragment mass distributions is discussed, where it is shown that massasymmetric structure remaining at high excitation energies originates from low-excited nuclei by evaporation of neutrons. [ABSTRACT FROM AUTHOR]