1. Decay studies of exotic nuclei Krzysztof P. Rykaczewski Physics Division, Oak Ridge National Laboratory Oak Ridge, Tennessee exotic nuclei: - fission products of 238 U - super heavy nuclei produced in hot fusion

2. It is my first trip to Japan but I had several joint publications with Japanese collaborators before: “Beta decay of 20 Mg”, Nucl. Phys. A 584, 509, 1995 with S. Kubono and T. Nakamura GANIL LISE exp in 1991 decay data relevant for the break-out from CNO cycle several papers from 1998 to 2004 with M. Shibata Total Absorption Spectroscopy at GSI ISOL facility performed with M. Nitschke’s (Berkeley) TAS by Warsaw -Valencia-GSI teams “True Gamow-Teller strength distribution around 100 Sn and 146 Gd”

3. many results on new and important  s-isomers obtained afterwards at GANIL (LISE), GSI (FRS), NSCL(A1900) and more recently at RIKEN see, e.g., Kameda, Kubo,.. et al, PR C86, 054319, 2012 Early work in GANIL on 20 Mg triggered the expansion of GSI ISOL program of Gamow-Teller β-transitions studies near 100 Sn to fragmentation reactions. It resulted the identification and studies of  s-isomers R. Grzywacz et al.,Phys. Lett. B 355, 439,1995; PR C55, 1126, 1997; PRL 81, 766, 1998 R. Grzywacz et al., Phys. Rev.C55, 1126, 1997 R. Grzywacz et al., Phys. Lett. B355, 439, 1995

4. among motivations of the HRIBF decay studies of fission products : - understanding the evolution of nuclear structure -- single-particle levels around shell gaps -- beta strength function related to the structure of parent and daughter states - beta-decay data for the analysis of post r-process isotopic distributions and nuclear fuel cycle -- half-lives -- properties of beta-delayed neutron emission -- decay heat -- antineutrino energy spectra (deduced from true β-transition probabilities) -- low-energy states, isomers... HRIBF based decay studies of fission products substantially contributed to our understanding of neutron-rich nuclei

5. Holifield Radioactive Ion Beam Facility capable to produce and study nuclei at the neutron-rich and proton-rich limits of nuclear landscape IRIS-1 IRIS-2 ORIC lasers isobar separator Tandem RMS OLTF

6. = Holifield Radioactive Ion Beam Facility at Oak Ridge (1996 - 2012) proton-induced fission of 238 U creates a lot of neutron-rich nuclei for spectroscopic studies 86 Ga: HRIBF: ~10,000/hour at 15  A protons pure beam at the HRIBF ! RIKEN:10/hour at 0.2 pnA 238 U (now ~ 5 pnA) J.R. Beene et al., J. Phys. G: Nucl. Part. Phys. 38, 024002, 2010

7. Decay studies of fission products at the Range out experiment LeRIBSS experiment +/-40 keV +/-160 keV Isobar separator M/  M ~ 10000 Mass separator M/ΔM ~ 1000 54 MeV protons 12- 18  A 2-3 MeV/u 200 keV charge exchange cell (removes Zn, Cd) 0% - 40% efficiency typically 5% efficiency Positive ions Positive or negative ions Tandem accelerator (negative ions only) ~ 10% efficiency IRIS-1 ORIC : ~6 g 238 U fission fragments ~10 11 /s         ~7 %   ~70% gas cell IRIS-1 and IRIS-2, laser ionization beam kicker Energy loss Total ion energy 76 Cu 76 Ga 76 Ge no 76 Zn !!! Range out exp gas cell spectra C.J.Gross et al., EPJ A25,115,2005

8. two-stage magnetic separation: from molecular beams like A=118 86 Ge 32 S + to pure “nominal mass A - ” ion beam example: new 84-86 Ge, 84-87 As - results A variety of beam purification methods selective laser ionization

9. Detectors for beta decay studies CARDS β-  at LeRIBSS VANDLE n-TOF array at LeRIBSS Hybrid 3Hen-β-  array at LeRIBSS ε n ~30% 3Hen array after “ranging-out” 850 liters of 3 He at 10 atm ε n ~80% Ed Zganjar, LSU Robert Grzywacz, UTK

10. nearly 80% efficient and segmented 3 Hen neutron counter ORNL, UTK LSU, Mississippi UNIRIB 850 liters of 3 He at 10 atm ε n ~80%

11. Detectors for beta decay studies 2200 pounds of NaI(Tl) - Modular Total Absorption Spectrometer (MTAS) and its 12,000 pound shielding Decays studied at HRIBF Tandem-OLTF-MTAS are marked by yellow squares. Labels “1” and “2” indicate the priority for decay heat measurements established by the Nuclear Energy Agency (NEA) in 2007 January 2012

12. Beta decay of very neutron-rich nuclei is very rich in interesting features β  and MTAS neutron detection 3Hen, VANDLE

13. 22 parent radioactivities in 78 Ni region studied by means of β  spectroscopy at the HRIBF 78 Ni to 132 Sn region (~ 10), + MTAS (22), + VANDLE (29) 80 As 79 Ge 78 Ga 77 Zn 76 Cu 75 Ni 81 As 80 Ge 79 Ga 78 Zn 77 Cu 76 Ni 82 As 81 Ge 80 Ga 79 Zn 78 Cu 77 Ni 83 As 82 Ge 81 Ga 80 Zn 79 Cu 78 Ni 84 As 83 Ge 82 Ga 81 Zn 80 Cu 79 Ni 85 As 84 Ge 83 Ga 86 As 85 Ge 84 Ga 87 As 86 Ge 85 Ga 83 Se 84 Se 85 Se 86 Se 87 Se 88 Se 82 Zn 83 Zn Z=28 N=50 79 As 78 Ge 77 Ga 76 Zn 75 Cu 74 Ni 78 As 77 Ge 76 Ga 75 Zn 74 Cu 73 Ni 86 Ga 88 As 87 Ge 89 Se 77 As 76 Ge 75 Ga 74 Zn 73 Cu 72 Ni

14. D. Miller, R Grzywacz et al., to be published ~ 2 days exp detected 79 Cu ions: NSCL 2005 (2010): 754 HRIBF 2006: ~16 000 RIKEN 2010: ~ 10 000 HRIBF 2011: ~158 000 81 Zn 81 Ga 78 Ni 79 Cu 79 Zn initial yields : 79 Zn ~ 10 5 pps 79 Cu + ~ 40 pps after charge exchange : 79 Zn 0.0 pps 79 Cu - ~ 2 pps pure beam of 79 Cu ions → single neutron-hole states in N=49 79 Zn 78 Zn 79 Cu decay (HRIBF LeRIBSS) N=50 0.29(2) s half-life of 79 Cu Kratz 1991 : 188(25) ms (multi βn fit) Hosmer 2010 : 257(+ 29,- 26) ms (ion-β) Miller 2013: 290(20) ms (β-  730 keV)

15. Beta-delayed neutron emission: counting identified ions → absolute branching ratios HRIBF results pointed to much higher β-delayed neutron branching ratios in comparison to earlier measurements and calculations see, e.g., Pfeiffer, Kratz, Moeller (PKM 2002) Progress in Nucl. Energy, 41, 5 (2002) similar conclusions: P. Hosmer, H. Schatz et al., PR C82, 025806, 2010 J. Winger et al., PRL 102, 142501 (2009) PRC 80, 054304,2009; PRC 81,044303,2010; PRC 82, 064314 (2010); PRC 83, 014322 (2011); PRC 86, 024307,2012 all βn-precursors given in this plot have T 1/2 < 1 s

16. Delayed Neutron Yield following 235 U fission Integral β,n measurements used for reactor analysis  -n isotopic decay data ORIGEN is missing data for very short-lived fission products from Ian C. Gauld, ORNL Reactor Science Group (2010) Note log scales !

17. Example of MTAS data – 139 Xe decay (A. Fijałkowska et al., ND2013) ( 139 Xe ~5% cumulative fission yield for n th + 235 U) MTAS data (black) compared to ENDSF-based simulations (red). Lack of β-feeding and following  -energy release from highly excited states in current data base ! MTAS-revised decay of 139 Xe average  -energy release increased from 935 keV to 1146 keV (23%)

18. May 2010 : the Department of Energy creates the first nuclear energy innovation hub -- the Consortium for Advanced Simulation of Light Water Reactors (CASL) -- headquartered at Oak Ridge. The first task will be to develop computer models that simulate nuclear power plant operations, forming a "virtual reactor" for the predictive simulations of light water reactors. Other tasks include using computer models to reduce capital and operating costs per unit of energy, safely extending the lifetime of existing U.S. reactor and reducing nuclear waste volume generated by enabling higher fuel burn-ups. http://www.ornl.gov/sci/casl/ We should remember that even the very best simulations of nuclear fuel cycles require correct experimental input data. “Conquering nuclear pandemonium” KR’s Viewpoint in Physics, 3, 94, 2010 (credit to A. Algora et al., PRL 105, 202501, 2010)

19. 79 Cu, 81,82,83 Zn, 85,86 Ga, 86 Ge, 86,87 As..... β  spectroscopy - new beta decays 83 Ge 81 Zn 83 Ga 84 Ge 81 Ga 78 Ni 82 Zn 84 Ga 85 Ge 85 Ga 79 Cu 83 Zn 86 Ga 86 Ge 82 Ga 117 ms228 ms304 ms 93 ms 85 ms 226 ms 87 As 86 As 484 ms 494 ms 290 ms molecular beams GeS, AsS ~ 3 ions/s, April 2012 pure Ga beams from laser ion source and hybrid 3Hen array 861ms

20. Departing from 78 Ni into a deformed region β-half-lives of 84,85,86 Ge and 84,85,86,87 As isotopes C. Mazzocchi, KR, et al., → Phys. Rev. C87, 034315, 2013 I.N. Borzov’s DF3a+CQRPA

21. Exp half-lives → β-theory → r-process (HRIBF measurements → I.Borzov’s analysis → R.Surman’s modeling) experiment FRDM Moeller 2003 DF3a+CQRPA Borzov 2011 M. Madurga et al., Phys. Rev. Letters, 109, 112501, 2012 + post r-process abundances simulations with Moeller’sT 1/2 ’s simulations with Borzov’s T 1/2 ’s R. Surman 2012

22. Evolution of single-particle states beyond N=50 evolution of neutron 3s 1/2 vs 2d 5/2 states in N=51 isotones (N=58 sub-shell closure) see J. Dobaczewski’s global calculations along N=50 isotones in J. Winger, KR,.. et al., PR C 81, 044303, 2010 Emerging N=58 d 5/2 -s 1/2 subshell ? (energy of s 1/2 state dropping down towards d 5/2 gs for n-rich nuclei)

23. Neutron states in N=51 isotones, from Z=30 81 Zn to Z=50 101 Sn 1g 7/2 3s 1/2 2d 5/2 Darby, Grzywacz et al., PRL 105, 162502,2010 101 Sn- 103 Sn- 105 Sn... Padgett, Madurga, Grzywacz et al., 81 Zn decay,PR C82, 064314, 2010

24. Interesting experiment for RIKEN: 82 Cu β-decay to s 1/2 state in N=51 81 Zn ( 80,81,82 Cu β-decay experiments were accepted at the HRIBF, but...) 82 Cu Q β ~ 17 MeV T 1/2 ~ 60 ms 82 Zn 81 Zn N=51 S n ~ 5 MeV s 1/2 d 5/2 0+0+ (4-,5-) βnβn ~ 0.6 MeV with 100 part*nA of relativistic 238 U beam (RIKEN, FRIB ?) we can go for more ambitious study of 80 Co βn-decay to the s 1/2 excited state in N=51 79 Ni T.Ohnishi,T.Kubo.. JPSJ 2010 0.2 pnA 238 U

25. Beta-delayed multi-neutron emission Decay of N=55 86 Ga studied with “hybrid 3Hen” at LeRIBSS in April 2012. Pure and intense beams of 83,85,86 Ga isotopes were produced at the IRIS-2 RIB platform using laser ion source RILIS Y. Liu et al., Nucl. Instr. Meth. Phys. Res. B298, 5, 2013. pure beams: 100 pps of 85 Ga, ~ 1- 3 pps of 86 Ga

26. Summary Decay studies of fission products at the HRIBF created a lot of new and reliable data on fission products decays 1.High energy resolution measurements with pure beams of known intensities (when post accelerated) ranging-out technique and gamma-beta-conversion electron detectors → basic “high energy resolution” decay scheme +  n-branching ratio 2. Measurements with Modular Total Absorption Spectrometer MTAS MTAS energy spectra in segmented array → beta strength within  -window (decay heat) 3. Measurements involving 3Hen and VANDLE →  -delayed neutrons βn-intensities and βn-energy spectra /Robert Grzywacz/ → beta strength above neutron separation energy Combining high-res  -data, 3Hen, MTAS, VANDLE → determination of a full  -strength function and its consequences → comparison with theory and further development of modeling

27. 2008-2012 LeRIBSS – OLTF (MTAS) HRIBF campaigns ORNL : C.J. Gross, Y. Liu, T. Mendez, K. Miernik, KR, D. Shapira, D. Stracener UT Knoxville : R. Grzywacz, K.C. Goetz, M. Madurga, D. Miller, S. Paulauskas, S. Padgett, L. Cartegni, A. Fijałkowska, M. Al-Shudifat and C.R. Bingham ORAU/ORNL : C. Jost, M. Karny, M. Wolińska-Cichocka Mississippi : J. A. Winger, S. Ilyushkin Louisiana : Ed Zganjar, B.C. Rasco UNIRIB : J.C. Batchelder, S. H. Liu Vanderbilt : N. Brewer, J.H. Hamilton, J.K. Hwang, A. Ramayya, C. Goodin Warszawa : A. Korgul, C. Mazzocchi Kraków : W. Królas IAEA: I. Darby NSCL-MSU: S. Liddick + VANDLE collaboration (talk by R. Grzywacz) theoretical analysis : I.N. Borzov (JIHIR/Dubna/Obninsk), K. Sieja (Strasbourg), R. Surman(NY-JINA) R. Grzywacz (UTK), J. Dobaczewski (Warszawa/Jyväskylä)

28. Studies of Super Heavy Elements ORNL, Oak Ridge ~ 250 mg 252 Cf ~ 8  g 254 Es

29. J. Roberto et al., workshop on SHE studies at the Dubna SHE Factory College Station, TX, 12-13 th March 2013 about 12 mg to 15 mg of actinide material is needed for one SHE target

30. 243 Am/ 244 Cm/ 248 Cm seed material and its n-capture/decay path to 249 Bk, 252 Cf, 253,254 Es and 257 Fm

31. 2012 – a very good year for SHE studies ! see 278 113 among the “Inventions of the year 2012” according to Time magazine (most experiments were performed with ORNL-made actinide target materials) 16 (+25 TASCA)(+1 TASCA) Yu.Ts. Oganessian et al., PRL 104, 142501, 2010; PRL 108, 022502, 2012; PRL 109, 162501, 2012; PR C 87, 014302, 2013 and submitted to PR C. (+1 TASCA)

32. new experiments at SHIP (GSI Darmstadt) 248 Cm+ 54 Cr, 33 out of 140 days, April-May 2011 (also 2012), beam dose ~5*10 18 - search for isotopes of new element Z=120, 298,299 (120) 178,179 (T 1/2 ~ 3  s) - expected short  -decay half-life required ORNL/UTK fast digital electronics - cross section limit of about 560 femtobarn reached at ~ 400 pnA beam current dead time ~ 11  s dead time ~ 0.3  s UTK Digital Signal Processing Laboratory SHIP analog data acquisition recoil  GSI Annual Report 2011 (2012)

33. New ORNL-UTK detectors and digital data acquisition system MICRON detectors 128 x48 mm,1 mm strips 300  m DSSD 500  m single Si-veto matching DSSD design six 120 x 65 mm single Si 300  m Si-box MESYTEC lin-log preamps ISEG NIM HV XIA Pixie16 rev D (208 channels) Dell Power Edge (similar DAQ at SHIP Z=120 exp was serving PSSD+Si-box+MCPs) LF 250 flange

34. Preparations for experiment searching for 293 (118), 295 (118) and 296 (118) isotopes with ORNL’s mixed-Cf target, new ORNL/UTK detection system and 48 Ca beam at Dubna. (50% of 249 Cf, 35% of 251 Cf and 15% of 250 Cf and very low content of 252 Cf)

35. Experiment with 48 Ca beam and 240 Pu ORNL target material at Dubna T SF ~10-100  s ?

36. Staszczak, Baran, Nazarewicz; Phys. Rev. C 87, 024320, 2013 Spontaneous fission modes and lifetimes of superheavy nuclei in the nuclear density functional theory 284 Fl (4n, 240 Pu) 296 118 (3n, 251 Cf) only even-even nuclei plotted here ?

37. Summary for the SHE section: 1.Impressive SHE harvest in 2012 at JINR, GSI and RIKEN ! 2. ORNL-made actinide materials are used to make “SHE targets”. New mixed-Cf target can help to reach the heaviest atomic nuclei, the isotopes of element 118 3. Digital data acquisition system, initially developed for the studies of  s- proton emitters at the HRIBF RMS (R. Grzywacz et al., UTK Digital Pulse Processing Laboratory), continues to be a system of choice in other experiments including the synthesis of super-heavy nuclei and fragmentation-based spectroscopy. 4. Experiment s on new short-lived super heavy nuclei with 48 Ca beam ( 44 Ca, 40 Ca) and 240 Pu ( 239 Pu, 245 Cm, 248 Cm..) can help to connect nuclear mainland to the “Hot Fusion Island” and provide important data on fission/alpha competition.