1. Update on relevant proposals on beta-delayed neutron emission, recent experiments and evaluated data K.P. Rykaczewski Physics Division, ORNL Oak Ridge IAEA, 2 nd CRP βdn meeting, 23-27th March 2015 -BRIKEN experiment “Around 78 Ni” -ORNL MTAS experiment, March 2015 -New evaluated data “north-east” of 78 Ni

2. 2 NP Comparative Review 2013 Beta-delayed neutrons - BRIKEN at RIKEN BRIKEN: - 20 pnA of 345 MeV/A of 238 U beam and BigRIPS at RIKEN -nearly all 3He gas available for nuclear spectroscopy (~ 70% ORNL) -the most powerful ion implantation/decay Si-array AIDA

3. 3 NP Comparative Review 2013 BRIKEN status -Large collaboration formed in 2012-2013, construction proposal accepted at RIKEN in December 2013 C. Domingo-Pardo (IFIC Valencia, Spain) as a project speaker -Proposal to measure βn-emission around mass A=130 accepted in June 2014 (A, 6.5 days) - (G. Lorusso, F. Montez, A. Estrade, S. Nishimura) -Proposal to measure β1n/β2n emission between 76 Co and 92 Se accepted in Dec. 2014 (A, 4 days) (KR, J. L. Tain, R. Grzywacz, I. Dillmann, S. Nishimura) - First batch of 3He tubes from Oak Ridge received at RIKEN on 16 th March 2015 - Test run planned for the end of April 2015 (Jose L. Tain) Our motivation: 1.Provide new data important for understanding and predicting β1n and β2n (βxn) emission rates 2.Provide new data important for understanding and modeling r-process nucleosynthesis

4. 4 NP Comparative Review 2013 Nuclear Chemistry Gordon Conference, 2013 Important physics case: β-strength (Gamow-Teller vs first forbidden β-decays) and β1n - β2n competition P β1n and P β2n values as input for the r-process path analysis This “ 78 Ni and beyond” project is aiming in a determination of 20 new P β1n and 14 new P β2n values i.e., the discovery of 14 β2n emitters at the r-process path. The examples of the effects of GT to ff competition on Pn values in Cu and Zn isotopes [Borzov 2005]. Blue arrows indicate the range of Cu and Zn isotopes to be measured in our project.

5. Nuclear Chemistry Gordon Conference, 2013 β-strength distribution and β1n - β2n competition Nuclear Chemistry Gordon Conference, 2013 P β1n P β2n First forbidden transitions compete for a beta-feeding with Gamow-Teller ones and reduce βxn branching ratios β1n emission competes with β2n emission in full one-neutron emission window, (β1n is not occurring ONLY in the excitation energy window between 1n and 2n separation energies)

6. 6 NP Comparative Review 2013 P 1n and P 2n values predicted for “our” new nuclei comparison of Miernik’s EDM 2014 * ) vs Moeller’s QRPA 2003 Larger P 1n Lower P 2n * ) K. Miernik, PR C 90, 054306,2014

7. 7 NP Comparative Review 2013 K. Miernik, PR C 90, 054306,2014

8. 8 NP Comparative Review 2013 K. Miernik, PR C 90, 054306,2014

9. 9 NP Comparative Review 2013 K. Miernik, PR C 90, 054306,2014

10. 10 NP Comparative Review 2013 β1n and β2n emitter 86 Ga Miernik et al., PRL 111,132502,2013 exp Moeller 2003 Borzov 2013 Kawano (ENDF VII) Miernik βn - PR C88, 2013 FRDM+QRPA DF3a+CQRPA (Moeller + CGM) βxn – PR C90, 2014 β1n 60(10)% 21% 20% 71% 53% β2n 20(10)% 44% 12% 5% 22% pre-dictions “post-dictions” More data points than just one single value are needed to guide/develop reliable theoretical descriptions of β1n/β2n rates. 14 new values of β1n/β2n should result from proposed experiment. R. Grzywacz + I. Borzov

11. β-delayed neutron emission in a cold r-process R. Surman cold r-process: equilibrium between (n, γ ) and β decay β-delayed neutron emission during supernova type cold r-process R. Surman, at Gordon conf., June 2013, at ARIS conf., June 2014 mass post r-process abundances Y(A) without beta-delayed neutrons with β-delayed neutrons in r-process neutron density

12. 12 NP Comparative Review 2013 Sensitivity of isobaric post r-process abundances to Pn values in the region of 78 < A < 100 nuclei (R. Surman 2014 ) Weak r-process trajectory [Panov&Janka2009 ], found in ejecta of NS-NS merger, with low entropy per baryon s/k=20 [Wanajo2014], low electron fraction Ye=0.35, and fast dynamic timescale, τ =50 ms, ρ(t) = ρ 0 x exp(-3t/ τ ) P1n(max) = ½ P0n + P1n + ½(P2n+P3n), P0n, P2n and P3n at 50% of Moeller’s values P xn – Moeller P 1n = 0 P 1n maximized The effect of βn-emission in the 78 < A < 100 nuclei is seen in Y(A) at higher masses

13. 13 NP Comparative Review 2013 Sensitivity measure F to the changes in P1n branching ratio [Surman2014]. The squares in different colors indicate the total change in ALL r-process abundances X(A), obtained by maximizing ONE P 1n value for a given nucleus, with respect to the calculations using baseline P 1n

14. 14 NP Comparative Review 2013 Predicted P β1n and P β2n values listed according to Moeller 2003 Region of interest (2 Big RIPS settings) Experimental P β1n values are given in black Present reach of 3 days exp at RIKEN with 238 U 25 pnA/345 MeV/u and BRIKEN βn-array

15. 15 NP Comparative Review 2013 78 Ni/ 79 Ni/ 81 Cu 82 Cu/ 84 Zn/ 86 Ga 85 Zn/ 87 Ga/ 89 Ge Predicted P β1n, P β2n and P β3n values listed according to Moeller 2003 Expected reach of FRIB and BRIKEN-like βn-array in 2022 35% 22% 29% 65% 10% 8%

16. SUMMARY for “Around 78 Ni” BRIKEN proposal BRIKEN collaboration is intending to measure β-delayed neutron emission in the ” 78 Ni and beyond“ part of nuclear chart, which is a starting region of the r-process. We will get a large set of new P β1n (20 ) and P β2n (14) experimental values allowing us to analyze and understand better the GT vs ff β-strength distribution and β1n – β2n competition. from spherical ( 78 Ni) to deformed ( 91 As) emitters 85 Ga, 86 Ga and 87 Ga predicted by Moeller to exhibit β3n emission are within our settings (but let first understand the β1n – β2n competition) Much more reliable input data for the r-process analysis affecting the abundances of nuclei created in the weak- r-process and affecting the later stages of main r-process. SUMMARY for “hybrid-3Hen + ranging-out” proposal at TRIUMF - Proposal to study bn-emitters accepted in 2013, but a Canadian’s permit to transfer 3He tubes for about 10 km on Canadian soil (Vancouver airport to TRIUMF laboratory) was not granted - Proposal status changed to “Letter of Intent” at the end of 2014

17. 17 NP Comparative Review 2013 M/ΔM~600 New (and earlier) experiments with Modular Total Absorption Spectrometer MTAS and pure beams at ORNL (March 2 nd -20 th, 2015)

18. 18 NP Comparative Review 2013 Priority “1” 139 Xe → 139 Cs decay (T 1/2 = 39.7 s) cumulative yield of 139 Xe in n th + 235 U fission is about 5% (ENDF/B-VII.1) MTAS result: average gamma energy release per 139 Xe decay increased from 935 keV to 1370 keV 46.5 % increase average beta energy release per 139 Xe decay decreased from1774 keV to 1573 keV 13% decrease 18 new  ’s and 11 new β-fed levels added to 139 Xe decay scheme 240  -lines populating 63 levels known from 139 Xe decay MTAS Aleksandra Fijałkowska et al., Nuclear Data Sheets 120, 26 (2014)

19. 19 NP Comparative Review 2013 Modular construction of MTAS helps to validate results ! Measured and modified 139 Xe decay in central and inner rings of MTAS see also Rasco et al., ARIS 2014 proceedings

20. 20 NP Comparative Review 2013 In 139 Xe decay, the average anti-neutrino energy is shifted down from 2240 keV (ENSDF) to 2014 keV (MTAS), i.e., by 226 keV Electron and anti-neutrino energy spectra in 139 Xe decay Energy spectrum of electrons ENSDF MTAS ENSDF MTAS Energy spectrum of anti-neutrinos Fijałkowska, Karny, et al., 2015

21. 21 NP Comparative Review 2013 Anti-neutrino interactions with protons ν+ p →n + e + High energy anti-neutrinos have higher cross section for the interactions with protons, i.e., have higher probability to be removed from ν beam. For anti-neutrinos with energies below 1.8 MeV energy threshold: no interactions on protons. anti-neutrino energy (MeV) cross section (10 -41 cm 2 ) energy threshold 1.8 MeV A. Strumia and F. Vissani, PL B 564, 42, 2003 σ (ν+ p) ~ (E ν ) 2

22. 22 NP Comparative Review 2013 Number of interactions of 89 Kr and 139 Xe anti-neutrinos per 10 keV energy bin (in % x 10 -43 cm 2 units). Interacting anti-neutrinos emitted in 89 Kr and 139 Xe decay 89 Kr 139 Xe ENSDF MTAS ENSDF MTAS MTAS results for 89 Kr and 139 Xe decays account for 2.9 of the “missing 6% ” difference in the reactor anti-neutrino anomaly for a fresh nuclear fuel load, and for 1.8 and 1.5 out of the missing 6% for the burn-up phases corresponding to 2% FIMA and 3% FIMA, respectively, if applied to the anti-neutrino anomaly as calculated from all data contained in ENSDF. 41 % ↓ 21 % ↓ reactor antineutrino anomaly 94.3(23) % ~ 6 % missing

23. 23 NP Comparative Review 2013 40 MeV, 50 enA proton beam on 238 U MTAS on-line to the ORNL mass separator OLTF (On-line Test Facility = ISOL, m/Δm~600) Data acquisition based on digital pulse processing and using XIA Pixie16 modules (100 MHz) March 2015 Ge detector for monitoring collection point MTC Pixie16 Reference NaI(Tl) crystal with pulsed blue laser light for monitoring amplification changes. Laser light was split between reference and central/inner ring detectors. K. C. Goetz, R Grzywacz (UTK)

24. 24 NP Comparative Review 2013 New experiments with Modular Total Absorption Spectrometer MTAS and pure beams at ORNL (March 2 nd -20 th, 2015) Green – MTAS measurements with pure Bromine beams from LaB6 source Blue – MTAS measurements with Rb/Sr beams from surface ionized ion source ORNL’s Tandem-mass separator OLTF –MTAS βn emitters

25. 25 NP Comparative Review 2013 New experiments with Modular Total Absorption Spectrometer MTAS and pure beams at ORNL (March 2 nd -20 th, 2015) βn emitters Green – MTAS measurements with pure Bromine beams from LaB6 source Blue – MTAS measurements with Cs beams from surface ionized ion source ORNL’s Tandem-mass separator OLTF –MTAS

26. 26 NP Comparative Review 2013 85 Br→ 85 Kr decay (Q β =2.9MeV) measured with Tandem-OLTF-MTAS MTAS simulated spectrum following ENSDF data New levels fed in β-decay MTAS experimental spectrum 03/02/2015 Energy ( keV) These new high energy levels in 85 Kr fed by 85 Br β-decay were identified to de-excite to the 0.3 MeV isomeric level through the analysis profiting from MTAS segmentation. Central Inner Middle Outer MTA S

27. 27 NP Comparative Review 2013 MTAS results for 85 Br New levels fed in β-decay MTAS experimental spectrum 03/02/2015 γ-energy in single outer/middle modules Total MTAS energy (keV) counts - Central Inner Middle Outer MTA S B.C. Rasco LSU

28. 28 NP Comparative Review 2013 Priority 1 88 Br→ 88 Kr β-decay (Q β = 9 MeV) measured at Tandem-OLTF-MTAS Energy ( keV) MTAS simulated spectrum following ENSDF data MTAS experimental spectrum 03/03/2015 From the comparison of experimental and simulated MTAS energy spectra one can see that the intensity of beta feeding to the first excited 2 + state at 775 keV is much lower than the ENSDF value ( note log scales in figures ). It means there are much less of high energy anti-neutrinos emitted in this decay and γ-decay heat value will be higher. 775 keV Much larger β-feeding to high energy states in 88 Kr 7 MeV

29. 29 NP Comparative Review 2013 Energy (keV) 90 Br→ 90 Kr β-decay (Q β =11 MeV) measured with Tandem-OLTF-MTAS Total MTAS simulated spectrum following ENSDF A. Fijalkowska (Warsaw) MTAS experimental spectrum 03/05/2015 Neutron induced 6.8-6.9 MeV peaks from (n,γ) reactions on Na and I in NaI(Tl) crystals of outer, middle and inner rings of MTAS. 90 Br βn~25% total MTAS central inner middle outer 90 Br is an example of beta-delayed neutron (βn) precursor studied with MTAS. Neutron induced peaks occur in outer, middle and inner ring crystals. Neutrons are slowing down in central detector, but are rarely captured there (smaller volume and fast neutrons). MTAS spectra for 90 Br are again pointing to the large β-feeding I β to the highly excited states up to neutron separation energy of 6.5 MeV in 90 Kr, much larger I β than listed in ENSDF data. High energy tail in MTAS central and total spectra indicates the presence β-transitions of large energy, e.g., to the gs or 2 + state in 90 Kr. S n ~ 6.5MeV B.C. Rasco (LSU) Central Inner Middle Outer MTA S

30. 30 NP Comparative Review 2013 91 Br→ 91 Kr β-decay (Q β =9.9 MeV) and 91 Br→ 90 Kr ~ 20% βn-decay (Q β -S n = 5.8 MeV) measured with Tandem-OLTF-MTAS Central Inner Middle Outer MTA S note color code change vs previous slides total MTAS 707 keV 2 + →0 + in 90 Kr 1362 keV (4 + ) →2 + in 90 Kr Neutron induced (6.8-6.9) MeV and (6.8-6.9 + 0.707) MeV peaks from (n,γ) and (n,γ+0.707 MeV) reactions in NaI(Tl) crystals of outer and middle MTAS rings Energy spectrum of central crystal gated by neutron peaks in outer and middle detectors 91 Br 0 keV 707 keV 1362keV 90 Kr βnβn B.C. Rasco (LSU)

31. 31 NP Comparative Review 2013 86 Ge and its decay products C. Mazzocchi et al., 2015 New evaluated data from HRIBF LeRIBSS exp with molecular GeS and AsS beams

32. 32 NP Comparative Review 2013 Decay of 86 Ge Miernik et al., PRL 2013 C. Mazzocchi et al., 2015

33. 33 NP Comparative Review 2013 86 As decay

34. 34 NP Comparative Review 2013 New evaluated data from HRIBF LeRIBSS exp with molecular GeS and AsS beams A. Korgul et al., 2015, beta-gamma and beta-delayed neutron – gamma emission after 87 As decay βnβn

35. 35 NP Comparative Review 2013 Structure of N=53 isotones A. Korgul et al., Phys. Rev. C 88, 044330 (2013). High-energy GT-states All GT decay of 83 Cu → 83 Zn will go through βn

36. 36 NP Comparative Review 2013 Summary - BRIKEN experiment “Around 78 Ni” two BRIKEN experiments are accepted at RIKEN, impressive set of new data on β1n- and β2n-emitters is expected, it looks like this time we can ship 3He detectors from ORNL to RIKEN (not yet for TRIUMF). - ORNL MTAS experiment, March 2015 New data on true β-strength function distribution for several Br/Kr, I/Xe and Rb/Sr decays were obtained with pure beams, including 88 Br, 136m,gs I and 140 Xe having priority 1 for decay heat simulation (NEA 2007), again showing the presence of “gaps in nuclear data”. Several β1n-emitters were measured with MTAS, segmentation allows for the analysis of the effects of βn-interaction with MTAS crystals, n-capture + γ energy deposition observed. - New evaluated data “north-east” of 78 Ni Decays of βn-emitters in A=86 and A=87 were studied at the HRIBF and evaluated, mixed message about shell model applicability to these n-rich nuclei.