Alex Dombos Michigan State University Nuclear and Particle Physics

Transcription

1 Nuclear Science and Security Consortium September Workshop and Advisory Board Meeting The impact of prompt neutron emission from fission fragments on the final abundance pattern of the astrophysical r-process Alex Dombos Michigan State University Nuclear and Particle Physics September 11-12, 2017

2 Overview - Research performed with mentor Matthew Mumpower at Los Alamos National Laboratory - Eight weeks - NSSC LANL Summer Program - Astrophysical r-process - Nuclear fission - Prompt neutron emission - r-process network calculation - Impact on the final abundance pattern of the r-process 2

3 Astrophysical r-process 3

4 Fission (Z, A) Time Evolution 4

5 Fission (Z, A) Time Evolution 5

6 Fission (Z L, A L ) (Z, A) (Z H, A H ) Time Evolution 6

7 Fission (Z L, A L ) (Z L, A L ) n (Z, A) (Z H, A H ) (Z H, A H ) Time Evolution 7

8 Fission (Z L, A L ) (Z L, A L ) n (Z L, A L ) (Z, A) (Z H, A H ) (Z H, A H ) (Z H, A H ) Time Evolution 8

9 Fission Yield (Fission Fragment Mass Distribution) T. Kodama, and K. Takahashi, Nucl. Phys. A 239 (1975) 489 9

10 Fission Yield (Fission Fragment Mass Distribution) 8 >< Z fission = P Z >: A fission = P Z P Y (Z, A) Z A P Y (Z, A) A A T. Kodama, and K. Takahashi, Nucl. Phys. A 239 (1975)

11 Fission Yield (Fission Fragment Mass Distribution) 11

12 Prompt Neutron Emission D. G. Madland, Nucl. Phys. A 772 (2006)

13 Prompt Neutron Emission R. J. Howerton, Nuclear Science and Engineering 62,

14 Modifying the Yields 14

15 Modifying the Yields Y(Z, A) 15

16 Modifying the Yields Y(Z, A-1) Y(Z, A) ( Y 0 (Z, A) =Y (Z, A)[1 P (1)] Y 0 (Z, A 1) = Y (Z, A 1) + Y (Z, A) P (1) 16

17 Modifying the Yields ( Y 0 (Z, A) =Y (Z, A)[1 P (1) P (2)] Y(Z, A-2) Y(Z, A-1) Y(Z, A) Y 0 (Z, A 2) = Y (Z, A 2) + Y (Z, A) P (2) 17

18 Modifying the Yields Y(Z, A-2) Y(Z, A-1) Y(Z, A) 8 apple < P Y 0 (Z, A) =Y (Z, A) 1 P (n) n>0 : Y 0 (Z, A n) =Y (Z, A n)+y (Z, A) P (n) 18

19 Modifying the Yields 8 >< Z fission = P Z >: A fission = P Z P Y (Z, A) Z A P Y (Z, A) A A 19

20 Modifying the Yields 8 >< Z fission = P Z >: A fission = P Z P Y (Z, A 0 ) Z AP 0 Y (Z, A 0 ) A 0 + total A 0 20

21 Modifying the Yields 21

22 Modifying the Yields 22

23 PRISM - Use the modified yields in an r-process network calculation, and investigate the impact on the final abundance pattern - Portable routines for integrated nucleosynthesis modeling - Developed by mentor Matthew Mumpower at Los Alamos National Laboratory T. M. Sprouse and M. R. Mumpower. In preparation,

24 Neutron-induced and β-delayed Fission 24

25 Neutron-induced and β-delayed Fission 25

26 Neutron-induced and β-delayed Fission 26

27 Neutron-induced and β-delayed Fission 27

28 Neutron-induced and β-delayed Fission Global impact impacts the entire final abundance pattern 28

29 Neutron-induced and β-delayed Fission Nonlinear certain regions are impacted while others are not 29

30 Neutron-induced and β-delayed Fission Peaks shift in mass number 30

31 Neutron-induced and β-delayed Fission Fine details 31

32 Conclusions - Prompt neutron emission from fission fragments impacts the fine details of final abundance pattern of the r-process. - This project will be continued and expanded upon by the FIRE (fission in r-process elements) collaboration, which uses state-of-the-art theory to explore the role of fission in the r-process, and includes scientists from the University of Notre Dame, North Carolina State University, Los Alamos National Laboratory, Brookhaven National Laboratory, and Lawrence Livermore National Laboratory. 32

33 Disclaimer This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE- NA Disclaimer: This presentation was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 33

34 Details of presentation: - Main focus to present your research to NSSC partners, sponsor, and the advisory board. - Keep in mind this will be a 15 minute presentation, with an additional 5 minutes for questions. - Please include mention of the NSSC Focus Areas and any Crosscutting Focus Areas you are working under - Highlight any lab collaborations involved in your research, with specific mention of lab and lab mentor. 34

35 Modifying the Yields Cf(0,f) Vorobyev (2001) 252 Cf(0,f) Zeynalov (2011) 252 Cf(0,f) Göök (2014) 252 Cf(0,f) Walsh (1977) 3.0 (A) A, Fragment Mass Number (Before Prompt Neutron Emission) total = X Z X Y (Z, A) (A) A 35

36 Abundance Weighted Timescale n, =,n = = P Z,A P Z,A P Z,A P Z,A Y (Z, A) N n h i Z,A Y (Z, A) P Z,A P Z,A Y (Z, A),n(Z, A)Y (Z, A) Y (Z, A) (Z, A)Y (Z, A) 36

37 Conservation of Energy r = M(Z, A) M L (Z L,A L ) M H (Z H,A H ) = T L (Z L,A L )+T H (Z H,A H )+E L(Z L,A L )+E H(Z H,A H ) (E n + S n ) = T total f + E total (E n + S n ) = ht total f i + he totali (E n + S n ) = htf total i + hex total n i + he total i (E n + S n ) = ht total f i + [hs n i + h i]+he total i (E n + S n ) - Eqn. 17 in Nuclear Physics A 772 (2006) by D.G. Madland - E r = Q value = total energy release in binary fission - <T f total > = average total fragment kinetic energy - <E total* > = average total fragment excitation energy - <Ex n total > = average total fragment neutron emission energy - <E γ total > = average total fragment gamma-ray emission energy - <S n > = average fragment neutron separation energy - <ε> = average center-of-mass energy of emitted neutrons - E n = kinetic energy of incident neutron - S n = neutron separation energy of compound nucleus 37

38 Conservation of Energy - E r = Q value = total energy release in binary fission - Binding energies from FRDM E r = M(Z, A) M L (Z L,A L ) M H (Z H,A H ) = X Z,A BE(Z, A) Y (Z, A) BE(Z c,a c ) - <T total f > = average total fragment kinetic energy - Phys. Rev. C 31, 1550 (1985) by V. E. Viola et al. - htf total +7.3 i = Z2 c A 1/3 c - <E total γ > = average total fragment gamma-ray emission energy - Annu. Rev. Nucl. Sci Vol 24 pages by D. C. Hoffman and M. M. Hoffman - he total i = A c

39 Conservation of Energy - <S n > = average fragment neutron separation energy - Binding energies from FRDM 2012 hs n i = X Z,A S n (Z, A) Y (Z, A) - <ε> = average center-of-mass energy of emitted neutrons - Annu. Rev. Nucl. Sci Vol 24 pages by D. C. Hoffman and M. M. Hoffman - h i 2.34 MeV - E n = kinetic energy of incident neutron - Assume thermal energies in r-process - he n i 0 - S n = neutron separation energy of compound nucleus - Binding energies from FRDM

40 Howerton Systematics - Based on a Taylor expansion about 235 U(n,f) at the threshold energy for fission E th - Tested against <ν> for isotopes from 229 Th to 249 Cf in Threshold energies calculated using binding energies from FRDM 2012 (Z, A, E n )= (2 ( 1) A+1 Z ( 1) Z ) (Z 92) (A 235) +( (A 235)) (E n E th ) th(z, A) = Z 2 /(A + 1) +0.2 (2 ( 1) A+1 Z ( 1) Z ) S n (Z, A + 1) 40

41 Neutron-induced Fission 41

42 Neutron-induced Fission 42

43 Neutron-induced Fission 43

44 Neutron-induced Fission Global impact impacts the entire final abundance pattern 44

45 Neutron-induced Fission Nonlinear certain regions are impacted while others are not 45

46 Neutron-induced Fission Fine details 46

47 β-delayed Fission 47

48 β-delayed Fission 48

49 β-delayed Fission 49

50 β-delayed Fission Peaks shift in mass number 50