Diabatic paths through the scission point in nuclear fission

Bertsch, G. F.; Younes, W.; Robledo, L. M.

doi:10.1103/physrevc.100.024607

Title: Diabatic paths through the scission point in nuclear fission

Abstract

An outstanding problem in the theory of nuclear fission is to understand the Hamiltonian dynamics at the scission point. In this work the fissioning nucleus is modeled in self-consistent mean-field theory as a set of generator coordinate method (GCM) configurations passing through the scission point. In contrast to previous methods, the configurations are constructed in the Hartree-Fock approximation with axially symmetric mean fields and using the K -partition numbers as additional constraints. The goal of this work is to find paths through the scission point where the overlaps between neighboring configurations are large. A measure of distance along the path is proposed that is insensitive to the division of the path into short segments. For most of the tested K partitions two shape degrees of freedom are adequate to define smooth paths. However, some of the configurations and candidate paths have sticking points where there are substantial changes in the many-body wave function, especially if quasiparticle excitations are present. The excitation energy deposited in fission fragments arising from thermal excitations in the pre-scission configurations is determined by tracking orbital occupation numbers along the scission paths. This allows us to assess the validity of the well-known scission-point statistical model, in whichmore »« less

Authors:

^[1]; Younes, W. ^[2]; Robledo, L. M. ^[3]

Univ. of Washington, Seattle, WA (United States). Inst. for Nuclear Theory
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Univ. Autónoma de Madrid (Spain)

Publication Date:: Fri Aug 09 00:00:00 EDT 2019

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA); Ministry of Economic Affairs and Digital Transformation of Spain (MINECO)

OSTI Identifier:: 1836219

Alternate Identifier(s):: OSTI ID: 1550571

Report Number(s):: LLNL-JRNL-771816
Journal ID: ISSN 2469-9985; 963447; TRN: US2300281

Grant/Contract Number:: AC52-07NA27344; AC02-05CH11231; FPA2015-65929; FIS2015-63770

Resource Type:: Accepted Manuscript

Journal Name:: Physical Review C

Additional Journal Information:: Journal Volume: 100; Journal Issue: 2; Journal ID: ISSN 2469-9985

Publisher:: American Physical Society (APS)

Country of Publication:: United States

Language:: English

Subject:: 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Fission; nuclear fragmentation; nucleon induced nuclear reactions; nuclear many-body theory; thermal & statistical models

Citation Formats


                    Bertsch, G. F., Younes, W., and Robledo, L. M. Diabatic paths through the scission point in nuclear fission.  United States: N. p., 2019. 
Web.  doi:10.1103/physrevc.100.024607.

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                    Bertsch, G. F., Younes, W., & Robledo, L. M. Diabatic paths through the scission point in nuclear fission.  United States.  https://doi.org/10.1103/physrevc.100.024607

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                    Bertsch, G. F., Younes, W., and Robledo, L. M. Fri .  
"Diabatic paths through the scission point in nuclear fission".  United States.  https://doi.org/10.1103/physrevc.100.024607.  https://www.osti.gov/servlets/purl/1836219.

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@article{osti_1836219,

  title        = {Diabatic paths through the scission point in nuclear fission},

  author       = {Bertsch, G. F. and Younes, W. and Robledo, L. M.},

  abstractNote = {An outstanding problem in the theory of nuclear fission is to understand the Hamiltonian dynamics at the scission point. In this work the fissioning nucleus is modeled in self-consistent mean-field theory as a set of generator coordinate method (GCM) configurations passing through the scission point. In contrast to previous methods, the configurations are constructed in the Hartree-Fock approximation with axially symmetric mean fields and using the K -partition numbers as additional constraints. The goal of this work is to find paths through the scission point where the overlaps between neighboring configurations are large. A measure of distance along the path is proposed that is insensitive to the division of the path into short segments. For most of the tested K partitions two shape degrees of freedom are adequate to define smooth paths. However, some of the configurations and candidate paths have sticking points where there are substantial changes in the many-body wave function, especially if quasiparticle excitations are present. The excitation energy deposited in fission fragments arising from thermal excitations in the pre-scission configurations is determined by tracking orbital occupation numbers along the scission paths. This allows us to assess the validity of the well-known scission-point statistical model, in which the scission process is assumed to be fully equilibrated up to the separated fission fragments. The nucleus 236U is taken as a representative example in the calculations.},

  doi          = {10.1103/physrevc.100.024607},

  journal      = {Physical Review C},

  number       = 2,

  volume       = 100,

  place        = {United States},

  year         = {Fri Aug 09 00:00:00 EDT 2019},

  month        = {Fri Aug 09 00:00:00 EDT 2019}

}

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Title: Diabatic paths through the scission point in nuclear fission

Abstract

Citation Formats

Quantum mechanical description of the intrinsic excitation of fissioning nuclei journal, December 1981

Scission dynamics with K partitions journal, June 2018

Scission Dynamics with K Partitions text, January 2018

Diagnosing diabatic effects on the available energy of stratified flows in inertial and non-inertial frames journal, December 2018

Microscopic and nonadiabatic Schrödinger equation derived from the generator coordinate method based on zero- and two-quasiparticle states journal, October 2011

Fission barriers in actinides in covariant density functional theory: The role of triaxiality journal, October 2010

Diabatic Mechanisms of Higher-Order Harmonic Generation in Solid-State Materials under High-Intensity Electric Fields text, January 2017

Diabaticity of nuclear motion: problems and perspectives journal, May 1993

Microscopic Theory of Nuclear Fission: A Review text, January 2015

Fluctuations in the $^{235}$U(n,f) cross section text, January 2018

Numerical search of discontinuities in self-consistent potential energy surfaces journal, October 2012

Fluctuations in the U 235 ( n , f ) cross section journal, July 2018

Nonadiabatic Quantum Chemistry—Past, Present, and Future journal, November 2011

Microscopic Phase-Space Exploration Modeling of Fm 258 Spontaneous Fission journal, April 2017

Fission fragment charge and mass distributions in Pu 239 ( n , f ) in the adiabatic nuclear energy density functional theory journal, May 2016

Microscopic theory of nuclear fission: a review journal, October 2016

Self-consistent mean-field models for nuclear structure journal, January 2003

Diabatic Mechanisms of Higher-Order Harmonic Generation in Solid-State Materials under High-Intensity Electric Fields journal, January 2016

Time-dependent quantum collective dynamics applied to nuclear fission journal, February 1991

New Kohn-Sham density functional based on microscopic nuclear and neutron matter equations of state journal, June 2013

Scission-point model of nuclear fission based on deformed-shell effects journal, November 1976

Collective coordinates, shape transitions and shape coexistence: a microscopic approach text, January 1998

Induced Fission of Pu 240 within a Real-Time Microscopic Framework journal, March 2016

Microscopic calculation of Pu 240 scission with a finite-range effective force journal, November 2009

Fission properties of the Barcelona-Catania-Paris-Madrid energy density functional journal, November 2013

Composite-particle decay widths by the generator coordinate method journal, April 2019

Dissipative diabatic dynamics: A shell-model approach to large-amplitude collective nuclear motion journal, November 1983

New statistical scission-point model to predict fission fragment observables journal, September 2015

Collective coordinates, shape transitions, and shape coexistence: A microscopic approach journal, December 1998

Microscopic description of the fission path with the Gogny interaction journal, August 2018

Self-consistent calculations of fission barriers in the Fm region journal, July 2002

Quantum mechanical description of the intrinsic excitation of fissioning nuclei
journal, December 1981

Scission dynamics with $K$ partitions
journal, June 2018

Scission Dynamics with K Partitions
text, January 2018

Diagnosing diabatic effects on the available energy of stratified flows in inertial and non-inertial frames
journal, December 2018

Microscopic and nonadiabatic Schrödinger equation derived from the generator coordinate method based on zero- and two-quasiparticle states
journal, October 2011

Fission barriers in actinides in covariant density functional theory: The role of triaxiality
journal, October 2010

Diabatic Mechanisms of Higher-Order Harmonic Generation in Solid-State Materials under High-Intensity Electric Fields
text, January 2017

Diabaticity of nuclear motion: problems and perspectives
journal, May 1993

Microscopic Theory of Nuclear Fission: A Review
text, January 2015

Fluctuations in the $^{235}$U(n,f) cross section
text, January 2018

Numerical search of discontinuities in self-consistent potential energy surfaces
journal, October 2012

Fluctuations in the ${}^{235}U$ ( $n$ , $f$ ) cross section
journal, July 2018

Nonadiabatic Quantum Chemistry—Past, Present, and Future
journal, November 2011

Microscopic Phase-Space Exploration Modeling of ${}^{258}{Fm}$ Spontaneous Fission
journal, April 2017

Fission fragment charge and mass distributions in ${}^{239}{Pu} (n, f)$ in the adiabatic nuclear energy density functional theory
journal, May 2016

Microscopic theory of nuclear fission: a review
journal, October 2016

Self-consistent mean-field models for nuclear structure
journal, January 2003

Diabatic Mechanisms of Higher-Order Harmonic Generation in Solid-State Materials under High-Intensity Electric Fields
journal, January 2016

Time-dependent quantum collective dynamics applied to nuclear fission
journal, February 1991

New Kohn-Sham density functional based on microscopic nuclear and neutron matter equations of state
journal, June 2013

Scission-point model of nuclear fission based on deformed-shell effects
journal, November 1976

Collective coordinates, shape transitions and shape coexistence: a microscopic approach
text, January 1998

Induced Fission of ${}^{240}{Pu}$ within a Real-Time Microscopic Framework
journal, March 2016

Microscopic calculation of ${}^{240}{Pu}$ scission with a finite-range effective force
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Fission properties of the Barcelona-Catania-Paris-Madrid energy density functional
journal, November 2013

Composite-particle decay widths by the generator coordinate method
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