T-REX [ TAMU Re accelerated EX otics ]

1. Pastina formation in low density nucleonic matter S. Wuenschel1, H. Zheng1. K. Hagel1, B. Meyer2, M. Barbui1, E-J Kim1,3, G. Roepke4 and J. B. Natowitz1 T-REX [ TAMU Reaccelerated EXotics] Barbecue Pit ??

2. Core-collapse supernovae K.Sumiyoshi, G. Roepke PRC 77, 055804 (2008) K.Sumiyoshi et al., Astrophys.J. 629, 922 (2005) Mass fraction X of light clusters for a post-bounce supernova core Density. electron fraction, and temperature profile of a 15 solar mass supernova at 150 ms after core bounce as function of the radius. cluster formation Influences neutrino flux

3. Clustering in the Skins of Leptodermous Systems 208Pb 1.4 x 10 -17 km Neutron Star ~ 20 km

4. Manifestations of Clustering in Nuclei ----- 1.Light Alpha Structure of Light Nuclei See Talks Hagel, Barbui

5. Figure 2. The alpha-particle cluster structure of the Hoyle-state in 12C, as predicted using FermionicMolecular Dynamics (M. Chernykh, et al., Phys. Rev. Lett. 98, 032501 (2007)). 7.67 MeV

6. 2. Alpha Decay of Heavy Elements Bender, NN2012 Proceedings Calculated Qα .

7. 3. Larger Cluster decay C Isotope Preformation probabilities 222Ra  208Pb +14C Has been observed

8. 4. “Long Range Particle” Ëmission in Fission ----Ternary Fission • Common “ternary fission” - the break up into two massive fragments with a third fragment emitted approximately perpendicular to the massive fragments* • The mass of this third fragment varies, but the decay is strongly dominated by the emission of alpha particles ~ 10 - 20 MeV

9. Light Particle Accompanied or “Ternary” Fission 252 Cf - Thesis Heeg, T U Darmstadt

11. Ternary fission Yields • Thesis data of U. Koester • nthinduced ternary fission of 242Pu • TU Berlin 1999

12. System Yp = 0.389

13. Some experimental facts about ternary fission • The probability of ternary fission relative to binary fission is very small (~1/1000)

14. ternary fission has been treated in a variety of models • Simultaneous, dual, neck fracturing[1] • Characterized by: • Neck radius parameter • Viscosity/surface tension • Barrier systematics for alpha decay[2] • Characterized by: • Fragment emission barrier height • Frequency of assault on barrier [2] G.K. Mehta, et al PRC 7, 373 (1973)

15. Dynamic process of third fragment formation at neck rupture • Can also been treated statistically • Third fragment forms from interacting nucleons • Evaporation of fragments from hot neck region[3] • TDHF nucleon associations[4] • Non-equilibrium fragment formation[5] [3] G.V ValskyYad.Fiz. 24, 270 (1976) ** [4] J.W. Negele et al. Phys. Rev. C 17, 1098(1978) [5] V.A RubchenyaYad.Fiz. 35, 576 (1982) ** (** unable to obtain these references)

16. Our approach to ternary fission • In hot nuclear systems we know fragment formation can be very successfully treated as coalescence of free nucleons into fragments. • Consider: • Ternary fission as a warm system (T=1-1.5 MeV) • The low density region between the forming heavy fragments as an unstable region containing nucleons • n/p ratio depending on initial composition + some diffusion [6] L. Qin Phys Rev Lett 108, 172701 (2012)

17. Formation of the equilibrium distribution • Using NSEC provided by B. Meyers at Clemson • Calculates the equilibrium concentration of fragments being formed from an infinite source, characterized by: • T (originally T<1MeV – extension provided to higher T) • Density • Yp – proton fraction of source

20. Challenges • NSEC code assumes • Infinite size source • Infinite time (always reaches equilibrium) • Infinite size source provides infinite nucleons to coalesce into large fragments (according to binding energy) • Infinite time removes effect of transient fissioning system

21. Nucleation • Nucleation codes ‘coalesce’ nucleons into clusters but are kinetic approaches including terms making process time dependent • Equilibrium Yield is modified by complementary erfc term dependent upon three primary variables Time, Rho, AC

22. Nucleation • Ac is the critical cluster size • A<Ac – fragments do not grow • A>Ac – fragments continue to grow • In function, serves as the dividing line below which equilibrium yield is not affected and above which the yield falls dramatically

26. Clustering in the Skins of Leptodermous Systems 208Pb 1.4 x 10 -17 km Neutron Star ~ 20 km

32. THANK YOU Pastina formation in low density nucleonic matter – a mechanism for ternary fission S. Wuenschel1, H. Zheng1. K. Hagel1, B. Meyer2, M. Barbui1, E-J Kim1,3, G. Roepke4 and J. B. Natowitz1 Ternary fission yields in the reaction 241Pu(nth,f) are calculated using a new model which assumes a nucleation-time moderated chemical equilibrium in the low density matter which constitutes the neck region of the scissioning system. The temperature, density, proton fraction and fission time required to fit the experimental data are derived and discussed. A reasonably good fit to the experimental data is obtained. This model provides a natural explanation for the observed yields of heavier isotopes relative to those of the lighter isotopes, the observation of low proton yields relative to 2H and 3H yields and the non-observation of 3He, all features which are shared by similar thermal neutron induced and spontaneously fissioning systems.

33. 241Pu Fit metric is short M: z<7

34. 245Cm Fit metric is short M: z<7

35. 249Cf Fit metric is short M: z<7 **NOTE: normalized at 14C

36. NSEC and Ternary Fission