Studies of mass and energy correlations in thermal neutron fission of U-235 accompanied by long range alpha particles

Abstract

Several characteristics of fission accompanied by long range alpha particles (LRA) have been studied in the thermal neutron induced fission of ²³⁵U. The kinetic energies of fission fragments and the LRA were measured with a back-to-back ionization chamber and semiconductor detectors respectively. The kinetic energies of the two fragments and the LRA in LRA fission, along with the energies of pair fragments in the normal binary fissions, were recorded event by event on a magnetic tape by means of a four-parameter data acquisition system. The data were analysed to study the dependence of different quantities in LRA fission on the fragment mass ratio, LRA energy and the total kinetic energy of the fission fragments. It is seen that the most probable energy of LRA increases significantly for near symmetric mass divisions. The total kinetic energy for all mass ratios in LRA fission is found to be (2.6±0.7) MeV larger than that in binary fission. The difference in the total kinetic energies in LRA and binary fissions is seen to be dependent on mass ratio. This result may suggest that the scission configuration in LRA fission is different for different mass ratios. Correlations between the fission fragment and LRA energies have been studied for several mass ratios. It is seen that the most probable fragment kinetic energy E _k varies nearly linearly with the LRA energy E_α for various mass divisions but the variation of the most probable LRA energy E _α with fragment kinetic energy E _k is found to deviate from linearity for several mass ratios. From a least square fit to the variation of E _k with E _α it is found that the slope (dE _k/dE_α) increases with the increase in mass ratio. The present results are discussed to arrive at a better understanding of the scission configuration in the fission accompanied by LRA emission.