Stylianos Nikas Central Michigan University

Transcription

1 Nuclear properties parameterization and implementation on Hauser-Feshbach statistical model based code Stylianos Nikas Central Michigan University In Collaboration with: George Perdikakis Rebecca Surman Mary Beard 1

2 Outline Motivation Description of calculations with the Hauser - Feshbach model Results-Example Summary 2

3 Motivation S. Liddick et al. Accepted PRL

4 Impact of the (n,γ) reaction rates in r - process nucleosynthesis Network calculations are sensitive to (n,γ) reaction rates Main mechanism to drive matter away of stability in neutron rich side Unable to measure the majority of these exotic nuclei - measurement of neutron capture rates are very difficult M. Mumpower et al

5 The Hauser - Feshbach model & the compound nucleus Cross section for reaction from channel a to channel b 5

6 The Hauser - Feshbach model & the compound nucleus Cross section for reaction from channel a to channel b Optical Potential Level Densities Gamma Strength Function Summation over all possible states Sum over all channels Transmission coeficients Mass Model Image credit: Hans Peter Loens, Thesis, Darmstadt

7 The Hauser - Feshbach model & the compound nucleus Cross section for reaction from channel a to channel b Optical Potential Level Densities Gamma Strength Function Summation over all possible states Sum over all channels Transmission coefficients Mass Model Tested by R. Surman & M. Mumpower Image credit: Hans Peter Loens, Thesis, Darmstadt

8 We used Talys 1.6 -Range of T = GK -Range of Z = Optical Model Koning-Delaroche JLM Calculation - Models Nuclear Level Density (LD) Constant Temperature matched to the Fermi Gas model (CT+BSFG) Back-shifted Fermi Gas model (BSFG) Generalized Superfluid model (GSM) Hartree-Fock using Skyrme force (HFS) Hartree-Fock-Bogoliubov (Skyrme force) +combinatorial method (HFBS-C) γ-ray Strength Functions (GSF) Kopecky-Uhl generalized Lorentzian (KU) Hartree-Fock BCS (HF-BCS) Hartree-Fock-Bogolyubov (HFB) Modified Lorentzian (Gor-ML) 8

9 An Example: 165 Eu M. Mumpower et al

10 An Example: 165 Eu M. Mumpower et al

11 Effects of LD and GSF 11

12 Effect of nuclear LD and GSF Using the compatible combinations we get a band ~2 orders of magnitude Closer to Jina-reaclib rates 12

13 Impact of NLD & GSF S. Liddick et. al Accepted at PRL 13

14 Effects of Excitation Energy Binning 14

15 Effects of Excitation Energy Binning 15

16 Effects of gamma-normalization 16

17 Effects of gamma-normalization 17

18 Effects of the Optical model

19 Summary For T<2GK Biggest effects (up to 3 orders of magnitude) : NLD, GSF Medium effects (1-2 orders of magnitude): Excitation energy binning Minor effects or no effects: Optical potential 19

20 Acknowledgment Collaborators Support George Perdikakis Rebecca Surman Mary Beard College of graduate studies 20

21 21

22 Impact of the optical model 22

23 Impact of the optical model 23

24 Nuclear Model sets Nuclear Mass Models Goriely Hartree-Fock-Bogoliubov Skyrme tables(hfb) Peter Moller s FRDM (2012) Optical Model Koning-Delaroche JLM Nuclear Level Density Constant Temperature matched to the Fermi Gas model (CT+BSFG) Back-shifted Fermi Gas model (BSFG) Generalized Superfluid model (GSM) Hartree-Fock using Skyrme force (HFS) Hartree-Fock-Bogoliubov (Skyrme force) +combinatorial method (HFBS-C) γ-ray Strength Functions Kopecky-Uhl generalized Lorentzian (KU) Hartree-Fock BCS (HF-BCS) Hartree-Fock-Bogolyubov (HFB) Modified Lorentzian (Gor-ML) Code implementations gnorm Normalization of only phenomenological models No Normalization Enforced normalization of all models equidistant Logarithmic binning of excitation Energy* Linear binning Pre-equilibrium Yes No For code implementation comparisons the default Nuclear model inputs for Talys 1.6 have been used *Logarithmic Excitation Energy binning in Talys 1.6 have been replaced in the newer version of Talys 1.8 by a new version of logarithmic binning because of some problems it had found 24in reproducing results of the Linear binning in low energies

25 Sources of uncertainties in a (n,γ) reaction rate calculation Nuclear Models Statistical Properties Code Implementation Level Densities Strength - functions Mass - Models Gamma - normalization Excitation energy Binning No significant contributions Optical Potential Other Studies already available Hauser - Feshbach statistical model (compound nucleus) Pre-equilibrium 25