1 / 37

Decay studies of exotic nuclei

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. It is my first trip to Japan

dessa
Download Presentation

Decay studies of exotic nuclei

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Decay studies of exotic nuclei Krzysztof P. Rykaczewski Physics Division, Oak Ridge National Laboratory Oak Ridge, Tennessee • exotic nuclei: • fission products of 238U • 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 20Mg”, 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 100Sn and 146Gd”

  3. Early work in GANIL on 20Mg triggered the expansion of GSI ISOL program of Gamow-Teller β-transitions studies near 100Sn 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 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

  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 ORIC Tandem IRIS-1 OLTF IRIS-2 RMS isobar separator lasers

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

  7. Decay studies of fission products at the C.J.Gross et al., EPJ A25,115,2005 76Cu b Range out exp gas cell spectra g no 76Zn !!! g Energy loss 76Ga b 76Ge Total ion energy g g IRIS-1 and IRIS-2, laser ionization IRIS-1 Mass separator M/ΔM ~ 1000 fission fragments ~1011/s charge exchange cell (removes Zn, Cd) 0% - 40% efficiency typically 5% efficiency Positive ions ~6 g 238U ORIC : 54 MeV protons 12- 18 mA +/-40 keV +/-160 keV eg~7 % eb ~70% Tandem accelerator (negative ions only) ~ 10% efficiency Isobar separator M/DM ~ 10000 Positive or negative ions 200 keV LeRIBSS experiment gas cell beam kicker Range out experiment 2-3 MeV/u

  8. A variety of beam purification methods selective laser ionization two-stage magnetic separation: from molecular beams like A=118 86Ge32S+ to pure “nominal mass A-” ion beam example: new 84-86Ge,84-87As-results

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

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

  11. Detectors for beta decay studies 2200 pounds of NaI(Tl) - Modular Total Absorption Spectrometer (MTAS) and its 12,000 pound shielding January 2012 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

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

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

  14. 79Cu decay (HRIBF LeRIBSS) 81Zn 79Cu 81Ga 78Ni N=50 ~ 2 days exp 79Zn 78Zn 0.29(2) s initial yields : 79Zn ~105pps79Cu+ ~ 40pps after charge exchange : 79Zn 0.0pps79Cu- ~ 2 pps pure beam of 79Cu ions → single neutron-hole states in N=49 79Zn detected 79Cu ions: NSCL 2005 (2010): 754 HRIBF 2006: ~16 000 RIKEN 2010: ~ 10 000 HRIBF 2011: ~158 000 half-life of 79Cu Kratz 1991 : 188(25) ms (multi βn fit) Hosmer 2010 : 257(+ 29,- 26) ms (ion-β) Miller 2013: 290(20) ms (β- 730 keV) D. Miller, R Grzywacz et al., to be published

  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) all βn-precursors given in this plot have T1/2 < 1 s 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 similar conclusions: P. Hosmer, H. Schatz et al., PR C82 , 025806, 2010

  16. Delayed Neutron Yield following235U fission Integral β,n measurements used for reactor analysis b-n isotopic decay data ORIGEN is missing data for very short-lived fission products Note log scales ! from Ian C. Gauld, ORNL Reactor Science Group (2010)

  17. Example of MTAS data – 139Xe decay (A. Fijałkowska et al., ND2013) (139Xe ~5% cumulative fission yield for nth+ 235U) 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 139Xe average -energy release increased from 935 keV to 1146 keV (23%)

  18. http://www.ornl.gov/sci/casl/ 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. 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. 86Ge 86Ga 81Zn 83Ga 84Ge 81Ga 78Ni 82Zn 84Ga 85Ge 85Ga 79Cu 83Zn β spectroscopy - new beta decays 79Cu, 81,82,83Zn, 85,86Ga, 86Ge, 86,87As ..... molecular beams GeS, AsS 861ms 484 ms 86As 87As 494 ms 226 ms 83Ge 93 ms 85 ms 82Ga 304 ms 228 ms 117 ms 290 ms ~ 3 ions/s, April 2012 pure Ga beams from laser ion source and hybrid 3Hen array

  20. Departing from 78Ni into a deformed region β-half-lives of 84,85,86Geand84,85,86,87Asisotopes 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) M. Madurga et al., Phys. Rev. Letters, 109, 112501, 2012 R. Surman 2012 + post r-process abundances simulations with Moeller’sT1/2’s experiment FRDM Moeller 2003 simulations with Borzov’s T1/2’s DF3a+CQRPA Borzov 2011

  22. Evolution of single-particle states beyond N=50 • evolution of neutron 3s1/2 vs 2d5/2 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 d5/2-s1/2 subshell ? (energy of s1/2 state dropping down towards d5/2 gs for n-rich nuclei)

  23. Neutron states in N=51 isotones, from Z=30 81Zn to Z=50 101Sn n1g7/2 n3s1/2 n2d5/2 Darby, Grzywacz et al., PRL 105, 162502,2010 101Sn-103Sn-105Sn ... Padgett , Madurga, Grzywacz et al., 81Zn decay,PR C82, 064314, 2010

  24. Interesting experiment for RIKEN: 82Cu β-decay to s1/2 state in N=51 81Zn ( 80,81,82Cu β-decay experiments were accepted at the HRIBF, but ...) T.Ohnishi,T.Kubo .. JPSJ 2010 0.2 pnA 238U 82Cu (4-,5-) Qβ~ 17 MeV T1/2 ~ 60 ms βn ~ 0.6 MeV s1/2 Sn~ 5 MeV d5/2 81Zn N=51 0+ 82Zn with 100 part*nA of relativistic 238U beam (RIKEN, FRIB ?) we can go for more ambitious study of 80Coβn-decay to the s1/2 excited state in N=5179Ni 

  25. Beta-delayed multi-neutron emission Decay of N=55 86Ga studied with “hybrid 3Hen” at LeRIBSS in April 2012. Pure and intense beams of 83,85,86Ga 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 85Ga, ~ 1- 3 pps of 86Ga

  26. Summary Decay studies of fission products at the HRIBF created a lot of new and reliable data on fission products decays • 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 + bn-branching ratio • 2. Measurements with Modular Total Absorption Spectrometer MTAS • MTAS energy spectra in segmented array • → beta strength within bg-window (decay heat) • 3. Measurements involving 3Hen and VANDLE → b-delayed neutrons • βn-intensities and βn-energy spectra/Robert Grzywacz/ • → beta strength above neutron separation energy • Combining high-res g-data, 3Hen, MTAS, VANDLE • → determination of a full b-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. KrólasIAEA: 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 252Cf ~ 8 g 254Es

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

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

  31. 2012 – a very good year for SHE studies ! see 278113 among the “Inventions of the year 2012” according to Time magazine (most experiments were performed with ORNL-made actinide target materials) 16 (+1 TASCA) (+25 TASCA) (+1 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.

  32. new experiments at SHIP (GSI Darmstadt) • 248Cm+54Cr,33 out of 140 days, April-May 2011 (also 2012), beam dose ~5*1018 • - search for isotopes of new element Z=120, 298,299(120)178,179 (T1/2 ~ 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 GSI Annual Report 2011 (2012) SHIP analog data acquisition dead time ~ 11 s  UTK Digital Signal Processing Laboratory recoil recoil dead time ~ 0.3 s

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

  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 48Ca beam at Dubna. (50% of 249Cf, 35% of 251Cf and 15% of 250Cf and very low content of 252Cf)

  35. Experiment with 48Ca beam and 240Pu ORNL target material at Dubna TSF ~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 only even-even nuclei plotted here ? 284Fl (4n,240Pu) 296118 (3n,251Cf)

  37. Summary for the SHE section: • 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 48Ca beam (44Ca, 40Ca) and 240Pu (239Pu, 245Cm, 248Cm..) • can help to connect nuclear mainland to the “Hot Fusion Island” • and provide important data on fission/alpha competition.

More Related