Effects of microscopic transport coefficients on fission observables calculated by Langevin equation and its systematics

Abstract

Abstract. The Langevin dynamical description of fission observables is inspired by the random evolution of shape parameters across the potential surface. In these work, we shall use mass and friction tensors inspired from Linear Response Theory (microscopic transport coefficients) and obtain the fission observables associated with these calculations. We compare these microscopic results with calculations using hydrodynamical mass tensor and wall-window friction tensor (macroscopic transport coefficients). We are able to calculate the fission product yield, Coulomb kinetic energy and prescission kinetic energy from the Langevin calculation. This allows us to observe the systematic of average light and heavy mass fission product yield calculated using both microscopic and macroscopic calculations. We also compare the results of microscopic and macroscopic calculation total kinetic energy (TKE) with Viola's TKE systematics. In the case of 236,239 U compound nucleus, we do the microscopic calculation for several excitation energy up to 30 MeV and afterwards compare it to the TKE of experimental data and corresponding macroscopic TKE. Reasonable agreement of microscopic TKE to experiment is obtained which shows decreasing TKE with increasing excitation energy. Macroscopic TKE however, is independent of excitation energy and thus contrary to experimental data.

Analysis of the total kinetic energy of fission fragments with the Langevin equation

“…Such an increasing trend of TKE at low E n values is reproduced, although not perfectly, by the present Langevin calculation with microscopic transport coefficients. In contrast, results from our Langevin calculation with macroscopic transport coefficients [46] are approximately constant, giving an average TKE of 167.5 MeV irrespective of E n . We can see that in comparison to results with macroscopic transport coefficients, those with the microscopic transport coefficients are much closer to the trend of experimental pre-neutron data and behave similarly with higher E n .…”

“…We also plot 256,258 Fm experimental results from [44] (open squares) and [45] (filled squares). We compare them with (a) our previous data [46,47] (blue inverted triangles) for compound nucleus at Ex = 20 MeV.…”

“…We compare also with several other nuclides using our previous results at Ex = 20 MeV [46,47] for (f) microscopic and (g) macroscopic transport coefficients. [46] calculations with macroscopic transport coefficients without using the effective temperature description in Eq. ( 10), (b) experimental data from [50], and (c) experimental data from [58].…”

“…In Fig. 5 we collected the results of present calculations for 236 U at E x =6.545 and 20 MeV, and for 254,256,258 Fm at 1 MeV above the second fission barrier B f 2 , together with the data from our previous calculations [46,47] and experimental mass averages. The barriers B f 2 are obtained from generic calculations using the GEF code [42].…”

“…Included are (c) evaluated data from JENDL [43] and experimental spontaneous TKE from (d) [55] and (e) [56]. We compare also with several other nuclides using our previous results at Ex = 20 MeV [46,47] for (f) microscopic and (g) macroscopic transport coefficients. [46] calculations with macroscopic transport coefficients without using the effective temperature description in Eq.…”