Dynamical study of fission process and estimation of prescission neutron multiplicity

Abstract

The dynamics of fission has been studied by solving Euler-Lagrange equations with dissipation generated through one and two body nuclear friction. The average kinetic energies of the fission fragments, prescission neutron multiplicities and the mean energies of the prescission neutrons have been calculated and compared with experimental values and they agree quite well. A single value of friction coefficient has been used to reproduce the experimental data for both symmetric and asymmetric splitting of the fissioning systems over a wide range of masses and excitation energies. It has been observed that a stronger friction is required in the saddle to scission region as compared to that in the ground state to saddle region.

Dissipative dynamics of fission in the framework of asymptotic expansion of Fokker-Planck equation

“…In the fission process, in accordance with our previous work [10], the shape of the fissioning nucleus is described in terms of the elongation axis (the neck parameter of [11] taken equal to zero). Thus, in the dynamical description we have the elongation axis, its relative orientation with respect to an inertial system and respective velocities associated with them as the stochastic variables interacting with a large number of internal nucleonic degrees of freedom constituting a heat bath at temperature T determined by the excitation energy available to it.…”

“…It has already been shown that the tangential friction which causes dissipation of relative angular momentum L into the angular momenta I 1 , I 2 of the two fragments does not have any significant effect on the physical observables [10] . Besides, no experimental observation of angular momentum dispersion of fission fragments are available in the litterature.…”

“…Here, we assumed that each fissioning nucleus in the ensemble starts from a fixed initial position but with different partioning of initial excitation energy [10]. Finally, substitution of Eq.…”

“…The initial conditions of r andṙ for solving Eq. (2.18) are [10] r 0 = r(t = 0) = r min ± δr 0 ,ṙ 0 =ṙ(t = 0) = (…”

“…The Euler-Lagrange equations (2.6) were solved in our earlier works [10]. To avoid repetition we deliberately omit the procedure and scheme to solve those equations.…”