Correlated Prompt Fission Data

Transcription

1 Correlated Prompt Fission Data Patrick Talou 1, T. Kawano 1, I. Stetcu 1, D. Neudecker 2 1 Theoretical Division, Los Alamos National Laboratory, USA 2 XCP-5, Computational Physics Division, Los Alamos National Laboratory, USA 14 th Int. Conference on Nuclear Reaction Mechanisms June 15-19, 2015, Varenna, Italy LA-UR

2 One Fission Event = Vast and Rich Data Set Complete fission event, from pre- to post-scission Focus on prompt fission data only Prompt Fission Neutrons & Photons Very important quantities for Applications: Neutrons: average spectrum and multiplicity + P(ν) for neutron multiplicity counting Photons: total γ-ray energy Fundamental Physics Everything! New experiments and new theoretical tools to address those data Slide 2

3 Theoretical Approach Hauser-Feshbach formalism applied to primary fission fragments Monte Carlo implementation à CGMF code Probability distributions for evaporating neutron or photon sampled at each stage of the decay Optical Model Calculation for neutrons γ-ray Strength Function for photons Nuclear structure information from RIPL-3 database Correlations & distributions accessible Important physics questions can be addressed Important applications cold fission Slide 3

4 Recent experimental efforts Prompt Fission Neutron Spectrum Chi-Nu (LANL), CEA-BRC, LiCORNE (Orsay), Gatchina IAEA-CRP on PFNS being finalized Prompt Fission γ rays DANCE (LANL, LLNL) IRMM Chi-Nu DANCE D. Neudecker, P. Talou, T. Kawano et al., Nucl. Inst. Methods in Phys. Research A 791, (2015) IRMM Gatchina Slide 4

5 Prompt Fission Neutron and Gamma Multiplicities <ν> very sensitive to <TKE>, <TKE>(A,Z) <N γ > very sensitive to energy threshold E cut Monte Carlo Hauser-Feshbach calculations are very successful in reproducing observed multiplicity average values and distributions! Slide 5

6 Total γ-ray Energy vs. TKE CGMF predictions for 252 Cf (sf) TXE = Q f TKE ' cm + B n + E tot Distinct structures appear due to regularity in neutron binding energies in fission fragments Recent DANCE experiment Analysis is ongoing Slide 6

7 Results for Specific Fragments γ-ray Spectra Specific γ transitions à study of isomeric ratios, fission yields, P(ν), etc. Hardening of γ spectra for near shell-closure nuclei CGMF calculations Experimental Results S. Oberstedt et al., P(ND)^2-2, Paris, Oct Slide 7

8 Results for Specific Fragments Exclusive neutron spectra Very good agreement for most fragments CGMF, α=1.7 IRMM 252 Cf(sf), A = 130 Discrepancies near shell closures φ(ε)/ ε 1e-05 1e-06 1e CMS Outgoing Neutron Energy (MeV) CGMF, α=1.7 IRMM φ(ε)/ ε e-05 1e Cf(sf), A = 121 CGMF, α=1.7 IRMM Slide 8 Experimental data from F.-J. Hambsch A. Göök, F.-J. Hambsch, and M. Vidali, Phys. Rev. C 90, 1e (2014) CMS Outgoing Operated Neutron by Energy Los Alamos (MeV) National Security, LLC for the U.S. Department of Energy's NNSA E φ(ε)/ ε 1e-05 1e Cf(sf), A = 130 1e CMS Outgoing Neutron Energy (MeV)

9 n-lf and n-n Angular Correlations Kinematic boost from FF n-lf angular distributions for different (ν L,ν H ) Slide 9

10 Incident Neutron-Induced Fission 235 U (n,f) and 239 Pu (n,f) up to 20 MeV Simplified model to calculate pre-neutron fission fragments Y(A,Z,TKE) Multi-chance fission Pre-equilibrium neutrons E

11 Implementation into MCNP6 Transport Code Integration of CGMF Monte Carlo Hauser- Feshbach code into MCNP6 Transport Code (in progress) Applications for detector response modeling, listmode data analysis, non-proliferation, and a better understanding of the fission process Slide 12

12 Open Questions Many quantities can be calculated accurately, but Calculated average PFNS too soft? Input data need improvement Fission fragment yields Y(A,Z,KE) as a function of E inc Nuclear structure of fission fragments Physics questions not fully settled Excitation energy sorting mechanism(s) at scission Scission neutrons? Angular momentum of the fragments Compensating errors? Slide 13

13 A powerful simulation tool for many interesting applications and physics questions Slide 14

14 Selected Publications Properties of prompt-fission gamma rays, I. Stetcu, P. Talou, T. Kawano, and M. Jandel, Phys. Rev. C 90, (2014). Isomer Production Ratios and the Angular Momentum Distribution of Fission Fragments, I. Stetcu, P. Talou, T. Kawano, and M. Jandel, Phys. Rev. C 88, (2013). Statistical and evaporation models for the neutron emission energy spectrum in the center-ofmass system from fission fragments, T. Kawano, P. Talou, I. Stetcu and M. B. Chadwick, Nuclear Physics A913, 51 (2013). Monte Carlo Hauser-Feshbach Predictions of Prompt Fission Gamma Rays - Application to n th U, n th Pu and 252 Cf (sf), B. Becker, P. Talou, T. Kawano, Y. Danon, and I. Stetcu, Phys. Rev. C 87, (2013). Advanced Monte Carlo Modeling of Prompt Fission Neutrons for Thermal and Fast Neutron- Induced Fission Reaction on Pu-239, P. Talou, B. Becker, T. Kawano, M. B. Chadwick and Y. Danon, Phys. Rev. C 83, (2011). Monte Carlo Simulation for Particle and Gamma-Ray Emissions in Statistical Hauser-Feshbach Model, T. Kawano, P. Talou, M. B. Chadwick, and T. Watanabe, J. Nucl. Sci. Tech. 47, No.5, 462 (2010). Slide 15