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Fission dynamics with microscopic level densities

Randrup, Jørgen LU ; Ward, Daniel LU ; Carlsson, Gillis LU ; Døssing, Thomas LU ; Möller, Peter LU and Åberg, Sven LU (2018) 4th Scientific Workshop on Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays, THEORY 2017 169.
Abstract

Working within the Langevin framework of nuclear shape dynamics, we study the dependence of the evolution on the degree of excitation. As the excitation energy of the fissioning system is increased, the pairing correlations and the shell effects diminish and the effective potential-energy surface becomes ever more liquid-drop like. This feature can be included in the treatment in a formally well-founded manner by using the local level densities as a basis for the shape evolution. This is particularly easy to understand and implement in the Metropolis treatment where the evolution is simulated by means of a random walk on the five-dimensional lattice of shapes for which the potential energy has been tabulated. Because the individual... (More)

Working within the Langevin framework of nuclear shape dynamics, we study the dependence of the evolution on the degree of excitation. As the excitation energy of the fissioning system is increased, the pairing correlations and the shell effects diminish and the effective potential-energy surface becomes ever more liquid-drop like. This feature can be included in the treatment in a formally well-founded manner by using the local level densities as a basis for the shape evolution. This is particularly easy to understand and implement in the Metropolis treatment where the evolution is simulated by means of a random walk on the five-dimensional lattice of shapes for which the potential energy has been tabulated. Because the individual steps between two neighboring lattice sites are decided on the basis of the ratio of the statistical weights, what is needed is the ratio of the local level densities for those shapes, evaluated at the associated local excitation energies. For this purpose, we adapt a recently developed combinatorial method for calculating level densities which employs the same single-particle levels as those that were used for the calculation of the pairing and shell contributions to the macroscopic-microscopic deformation-energy surface. For each nucleus under consideration, the level density (for a fixed total angular momentum) is calculated microscopically for each of the over five million shapes given in the three-quadratic-surface parametrization. This novel treatment, which introduces no new parameters, is illustrated for the fission fragment mass distributions for selected uranium and plutonium cases.

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author
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organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
host publication
Scientific Workshop on "Nuclear Fission and the Emission of Prompt Neutrons and Gamma Rays", THEORY 2017
volume
169
article number
00019
publisher
EDP Sciences
conference name
4th Scientific Workshop on Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays, THEORY 2017
conference location
Varna, Bulgaria
conference dates
2017-06-20 - 2017-06-22
external identifiers
  • scopus:85044003615
ISBN
9782759890316
DOI
10.1051/epjconf/201816900019
language
English
LU publication?
yes
id
61cd788f-6aad-4590-ab29-f9bc82f8aa6b
date added to LUP
2018-03-29 08:52:38
date last changed
2020-01-13 00:35:28
@inproceedings{61cd788f-6aad-4590-ab29-f9bc82f8aa6b,
  abstract     = {<p>Working within the Langevin framework of nuclear shape dynamics, we study the dependence of the evolution on the degree of excitation. As the excitation energy of the fissioning system is increased, the pairing correlations and the shell effects diminish and the effective potential-energy surface becomes ever more liquid-drop like. This feature can be included in the treatment in a formally well-founded manner by using the local level densities as a basis for the shape evolution. This is particularly easy to understand and implement in the Metropolis treatment where the evolution is simulated by means of a random walk on the five-dimensional lattice of shapes for which the potential energy has been tabulated. Because the individual steps between two neighboring lattice sites are decided on the basis of the ratio of the statistical weights, what is needed is the ratio of the local level densities for those shapes, evaluated at the associated local excitation energies. For this purpose, we adapt a recently developed combinatorial method for calculating level densities which employs the same single-particle levels as those that were used for the calculation of the pairing and shell contributions to the macroscopic-microscopic deformation-energy surface. For each nucleus under consideration, the level density (for a fixed total angular momentum) is calculated microscopically for each of the over five million shapes given in the three-quadratic-surface parametrization. This novel treatment, which introduces no new parameters, is illustrated for the fission fragment mass distributions for selected uranium and plutonium cases.</p>},
  author       = {Randrup, Jørgen and Ward, Daniel and Carlsson, Gillis and Døssing, Thomas and Möller, Peter and Åberg, Sven},
  booktitle    = {Scientific Workshop on "Nuclear Fission and the Emission of Prompt Neutrons and Gamma Rays", THEORY 2017},
  isbn         = {9782759890316},
  language     = {eng},
  month        = {03},
  publisher    = {EDP Sciences},
  title        = {Fission dynamics with microscopic level densities},
  url          = {http://dx.doi.org/10.1051/epjconf/201816900019},
  doi          = {10.1051/epjconf/201816900019},
  volume       = {169},
  year         = {2018},
}