Langevin description of mass distributions of fragments originating from the fission of excited nuclei

Vanin, D. V.; Nadtochy, P. N.; Kosenko, G. I.; Адеев, Г. Д.

doi:10.1134/1.1326976

Cited by 15 publications

(3 citation statements)

References 24 publications

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“…The SPW dissipation model was developed in 1985, but was not published outside of some relatively inaccessible conference proceedings [45,[75][76][77][78]. Despite its lack of wide dissemination, this dissipation model has been implemented by other authors [23,65,[79][80][81].…”

Section: Surface-plus-window Dissipationmentioning

confidence: 99%

Langevin model of low-energy fission

Sierk

2017

Phys. Rev. C

109

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Background: Since the earliest days of fission, stochastic models have been used to describe and model the process. For a quarter century, numerical solutions of Langevin equations have been used to model fission of highly excited nuclei, where microscopic potential-energy effects have been neglected. Purpose: In this paper I present a Langevin model for the fission of nuclei with low to medium excitation energies, for which microscopic effects in the potential energy cannot be ignored. Method: I solve Langevin equations in a five-dimensional space of nuclear deformations. The macroscopicmicroscopic potential energy from a global nuclear structure model well benchmarked to nuclear masses is tabulated on a mesh of approximately 10 7 points in this deformation space. The potential is defined continuously inside the mesh boundaries by use of a moving five-dimensional cubic spline approximation. Because of reflection symmetry, the effective mesh is nearly twice this size. For the inertia, I use a (possibly scaled) approximation to the inertia tensor defined by irrotational flow. A phenomenological dissipation tensor related to one-body dissipation is used. A normal-mode analysis of the dynamical system at the saddle point, and the assumption of quasi-equilibrium, provide distributions of initial conditions appropriate to low excitation energies, and is extended to model spontaneous fission. A dynamical model of post-scission fragment motion including dynamical deformations and separation allows the calculation of final mass and kinetic-energy distributions, along with other interesting quantities. Results: The model makes quantitative predictions for fragment mass and kinetic-energy yields, some of which are very close to measured ones. Varying the energy of the incident neutron for induced fission allows the prediction of energy dependences of fragment yields and average kinetic energies. With a simple approximation for spontaneous fission starting conditions, quantitative predictions are made for some observables which are close to measurements. Conclusions: This model is able to reproduce several mass and energy yield observables with a small number of physical parameters, some of which do not need to be varied after benchmarking to 235 U(n,f) to predict results for other fissioning isotopes.

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Section: Surface-plus-window Dissipationmentioning

confidence: 99%

Langevin model of low-energy fission

Sierk

2017

Phys. Rev. C

109

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“…The authors of Ref. [29] pointed out that anomaly large values of η(0), in the range of (2 -25)u, must be used in order to obtain a simultaneous description of the variances of mass distributions and multiplicities of prescission particles on the basis of both one-and two-body dissipations. The strong disagreement between the largest value η(0) = 25u obtained in this case and thoses given in other references mentioned above shed doubt on the posibility of consistently describing the mass-energy distribution and prescission-particle multiplicity.…”

Section: A Shear Viscosity At Zero Temperaturementioning

confidence: 99%

Shear-Viscosity to Entropy-Density Ratio from Giant Dipole Resonances in Hot Nuclei

Dang

2011

Preprint

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The Green-Kubo relation and fluctuation-dissipation theorem are employed to calculate the shear viscosity η of a finite hot nucleus directly from the width and energy of the giant dipole resonance (GDR) of this nucleus. The ratio η/s of shear viscosity η to entropy density s is extracted from the experimental systematics of the GDR in copper, tin and lead isotopes at finite temperature T . These empirical results are then compared with the predictions by several independent models, as well as with almost model-independent estimations. Based on these results, it is concluded that the ratio η/s in medium and heavy nuclei decreases with increasing temperature T to reach (1.3 − 4) × /(4πk B ) at T = 5 MeV.

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“…It should be mentioned that the multidimensional Fokker-Plank equation can only be solved by using approximate methods, while numerical solution of the multidimensional Langevin equations is almost possible without any approximations. One-dimensional Langevin calculations can yield fission probability and particle multiplicity and two-dimensional Langevin calculations make it possible to calculate the mass distribution of fission fragments that corresponds to the most probable kinetic energy [27,28] and energy distribution for symmetric fission [29][30][31]. Other features of the fission of heavy excited compound nuclei can be calculated on the basis of the three-and four-dimensional Langevin equations.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of different features of the fission process of excited nuclei in the framework of the modified statistical model and four-dimensional dynamical model

Eslamizadeh

2017

J. Phys. G: Nucl. Part. Phys.

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Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei and produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of was applied in the four-dimensional dynamical calculations. A comparison of the results of the three- and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, and the scaling factor of the fission-barrier height, .

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Langevin description of mass distributions of fragments originating from the fission of excited nuclei

Cited by 15 publications

References 24 publications

Langevin model of low-energy fission

Langevin model of low-energy fission

Shear-Viscosity to Entropy-Density Ratio from Giant Dipole Resonances in Hot Nuclei

Theoretical study of different features of the fission process of excited nuclei in the framework of the modified statistical model and four-dimensional dynamical model

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