Fragment Energy Correlation Measurements forCf252Spontaneous Fission and

Abstract

Fission-fragment mass and energy distributions and mass-versus-energy correlations have been obtained for 252 Cf spontaneous fission and 235 U thermal-neutron-induced fission. Silicon surface-barrier detectors were used in energy correlation measurements; absolute fragment energies were obtained by means of the massdependent energy calibration developed recently at this laboratory. Average total fragment kinetic energies before neutron emission are found to be 186.5±1.2 MeV for 252 Cf and 171.9dbl.4 MeV for 235 U. Detailed experimental results are given and compared with those of other experiments. Observed fine structure in the fragment mass distribution and in the average total fragment kinetic energy as a function of mass is correlated with the energetically preferred even-even nucleon configurations in the fragments. New determinations of the root-mean-square width of the total-kinetic-energy distribution as a function of mass show structure which is also correlated with the energetically preferred even-even fragment configurations. Fission-neutron and gamma-ray data of other experiments are used with the new fragment kinetic energies presented here to examine the total energy balance for fission for the two cases studied.

β-delayed fission of180Tl

“…These two assumptions are supported experimentally [1]. The average energy of the fragments after neutron emission can then be estimated by (neglecting the recoil energy [46])…”

“…If neutron emission occurs in the fission process, E i and m i are the quantities after neutron emission (postneutron quantities). E i and m i are the corresponding initial quantities, before neutron emission during fission, thus the preneutron quantities [46], and A f = 180 is the mass number of the fissioning 180 Hg nucleus. By using this calibration procedure it is only possible to calibrate coincident fission events, because the measured PH of both fission fragments will have to be inserted simultaneously in the above equations.…”

Polar light charged particles accompanying spontaneous fission

“…The final energy of fission fragments have been also taken from bipartition data [15]. Z(A) was parametrized by a smooth function obtained by partition of the neutron and proton numbers between two fragments what assured of being not too far from the stability path.…”

Generalized Energy-Dependent Q Values for Fission

“…One might assume that since fission is more sym- [10,11] show that EFR(A H ) is minimized near symmetric fission. This is a general feature of EFR that has been observed a number of times [10][11][12]. It is a result of several effects.…”