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HRIBF Now and in the Next Decade

HRIBF Now and in the Next Decade. ?. Jim Beene Witek Nazarewicz February 2008. The HRIBF now has capabilities that are unique worldwide Fission fragment (i.e. n-rich) beams above the CB We expect - and are seeing - improving reliability as HPTL / IRIS2 comes on line. HRIBF Today.

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HRIBF Now and in the Next Decade

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  1. HRIBF Now and in the Next Decade ? Jim Beene Witek Nazarewicz February 2008

  2. The HRIBF now has capabilities that are unique worldwide Fission fragment (i.e. n-rich) beams above the CB We expect - and are seeing - improving reliability as HPTL / IRIS2 comes on line HRIBF Today

  3. HRIBF 2008 25MV Tandem Electrostatic Accelerator Injector for Radioactive Ion Species 1 (IRIS1) Stable Ion Injector (ISIS) Oak Ridge Isochronous Cyclotron (ORIC) Enge Spectrograph Daresbury Recoil Separator (DRS) High Power Target Laboratory-HPTL: (IRIS2 2009) Recoil Mass Spectrometer (RMS) On-Line Test Facility (OLTF)

  4. Selected Highlights

  5. The first transfer measurements on N~82 nuclei on / near r-process path 132Sn(d,p)133Sn K. Jones 130Sn(d,p)131Sn - R. Kozub et al. 132Sn(d,p)133Sn - K.L. Jones et al. 134Te(d,p)135Te - S.D. Pain et al. • yields, angular distributions of low-lying states measured • first observation of p1/2 state in 133Sn • three other states in 133Sn measured, calibrated with 130Te(d,p) • evidence for numerous states in 131Sn never seen before • evidence that the f5/2 level in 135Te is at a significantly higher energy

  6. Superallowed -decay 109Xe →105Te →101Sn a Old standard (different shell structure for neutrons and protons) 213Po 209Pb • rp-process termination • en route to 104Te → 100Sn a 208Pb 208Pb a + n + + n New standard (the same shell structure for neutrons and protons) (5/2+) 620  70 ns a 100Sn 100Sn a n + + + n 105Te53 52 a 105Te 101Sn l=0 Identification at HRIBF of fastest known alpha decays: Ea = 4.703 keV (5/2+) 1.9 s S. Liddick et al., PRL 97,082501(2006) d2(105Te)/d2(213Po) =2.4(3) 101Sn51 50

  7. The evolution of shell structure in very neutron-rich nuclei beyond the N=50 shell closure b-decay studies around 78Ni with postaccelerated (3 MeV/u) pure neutron-rich RIBs beam T1/2 (s) main results 76Cu 0.65 bn-branching ratio Ibn 77Cu 0.46 Ibn, n- levels in N=47 77Zn 78Cu 0.35 Ibn, Ip of 78Cu49 revised 79Cu 0.19 bngdecay observed first time 83Ga 0.30 bng,bg, ns1/2 in N=51 83Ge 84Ga 0.08 2+ in N=52 84Ge 85Ga ??? rate of 0.1pps… • t1/2 & n rates for many r process nuclei are accessible • Energy levels test evolving nuclear structure • Range out unwanted high-Z contamination with high pressure & tape transport • Absolute beta-delayed neutron branching ratios for 76-79Cu and 83-84Ga • Identification of new excited states in 77Zn, 78Zn, 82Ge, 83Ge, and 84Ge • Systematics of single particle levels (e.g. neutron s1/2) near doubly magic 78Ni Winger et al.

  8. 76Cu no 76Zn !!! Energy loss 76Ga 75Zn 76Zn Total ion energy g 199 g 228 76Cu n b Ibn(76Cu)=6.9(4)% 76Zn76GaEg=199 keV 75Zn75GaEg=228 keV Gross et al., Eur. Phys. Jour. A 25, s01, 115, 2005 Winger et al., Acta Phys. Pol. B 39, No 2, 2008 Ilyushkin et al., World Scientific, 2008

  9. -decay of 109I and the rp-process Astrophysical relevance : C.Mazzocchi, …, H.Schatz,…PRL 98,212501 (2007) a p 109I → 105Sb →104Sn • No observable proton emission from 105Sb • The rp-process termination cycle starts at 105Sn • If 104Sb is much more proton bound than predicted (strong odd-even effect) it may start at 103Sn ! Sn-Sb-Te cycle ~10-2% Q=3918(21) keV Qp(105Sb)=356(22) keV ≠491(15) keV ? search for112Cs weak a-decay : SP of 108I and 104Sb rp-process termination H.Schatz et al., PRL86 (2001)

  10. 3000 134Sn/s Coulomb excitation in n-rich systemsPioneering Coulomb excitation of beams of radioactive isotopes of Ge, Sn, Sb, Te • Probing the evolution of collective motion in neutron-rich nuclei • Increasingly larger contributions of neutrons to B(E2) values above 132Sn • Recoil-in-Vacuum technique used to measure the g-factor for the first 2+ state in 132Te: Stone et al., PRL 94, 192501 (2005) Padilla-Rodal et al. Phys. Rev. Lett. 94, 122501 (2005) Yu et al., Eur. Phys. J. A 25, s01, 395 (2005) Radford et al., Nucl. Phys. A752, 264c (2005) Varner et al., Eur. Phys. J. A 25, s01, 391 (2005) Baktash et al., to be published

  11. Magnetic Moment Measurements of Short-Lived Excited States in a Radioactive Environment: 132Te • Transient field technique • 132Te beam slightly contaminated by 132Sb but both components are well separated in the gamma spectra • The sign of the g-factor determined (positive) The spectra show from top to bottom a typical γ singles spectrum (random spectrum), a coincidence cut on the prompt particle- time and the random-subtracted coincidence spectra for Clover segments at 138° and 58° with respect to the beam. The only peak left is the forward- or backward-Doppler shifted 2+ -> 0 transition in 132Te. In spite of a small true-to-random ratio, clean coincidence spectra can be obtained. N. Koller, G Kumbartzki et al.

  12. 80Se 666 keV 80Ge 659 keV This work, SIBs This work, RIBs Adopted value, S. Raman et al. Shell Model calculation Coulex of n-rich nuclei around A=80 at HRIBF Particle-g coincidence spectra RIB A=82 + 48Ti @ 220 MeV 82Se + 48Ti @ 220 MeV RIB A=78 + 12C @ 174.5 MeV RIB A=80 + 12C @ 179 MeV I = 1.4 x 106 pps 57.1% 78Ge, 28.1% 78Se, 9.9%78As, 4.9% 78Ga I = 1.4 x 105 pps 93.5% 80Ge, 2.2% 80Se I = 5.5 x 104 pps 19.2% 82Ge, 1.8% 82As, 79% 82Se Purified using AGeS+ E. Padilla-Rodal et al. PRL94, 122501 (2005)

  13. E. Padilla-Rodal et al. Sept. 2007

  14. Observation of fusion enhancement at sub-barrier energies in 134Sn+64Ni • Probing the influence of neutron excess on fusion at and below the Coulomb barrier • Large sub-barrier fusion enhancement has been observed • Inelastic excitation and neutron transfer play an important role in the observed fusion enhancement • Important for superheavy element synthesis • ERs made with 132,134Sn cannot be made with stable Sn http://www.phy.ornl.gov/theory/papenbro/workshop_Jan2008/Shapira.pdf Shapira et al., Eur. Phys. J. A 25, s01, 241 (2005) Liang et al., PRL 91, 15271 (2003); PRC 75, 054607 (2007)

  15. First Constraint on Very Low Temperature 18F(p, )15O reaction rate in Novae Kozub et al., PRC 71 (2005) 032801 Off resonance measurements provided first constraints on interference in the 18F+p system. HRIBF measurements reduced uncertainty in 18F(p,)15O rate reduced by ~30x 18F is -potentially important source of g-rays from novae -target of billion dollar orbiting telescopes 18F(p,)15O Chae et al., PRC 74 (2006) 012801. Bardayan et al., PRL 89 (2002) 262501.

  16. Direct Measurement of 17F + p 18Ne +  at ORNL HRIBF capture reaction intensity intensity 17F 17F 18Ne energy loss scattered 17O 17O scattered on resonance (600 keV) off resonance total energy • Proton capture on radioactive 17F - never before directly measured - is an important link in the • thermonuclear burning that powers nova explosions • Rate of this capture reaction needed to determine amount of radioactive 18F produced and the 17O / 18O ratio • Decay of radioactive 18F is searched for by satellite observatories, can constrain constrain nova explosion models • Previous attempts to indirectly determine this rate using beams of stable nuclei uncertain by orders of magnitude • Low energy beam of radioactive 17F • Intensity of over 15 million particles per second was sufficient to directly measure this weak reaction (a few counts / day) • Daresbury Recoil Separator used to directly detect the recoiling 18Ne from the capture reaction • Measurement completed February 2008; data currently under analysis, will be Ph.D. thesis for Kelly Chipps • First proton capture measurement on a radioactive beam in the U.S.; first U.S. facility [3rd worldwide] with this capability • New reaction rate will be used in explosion simulations to determine astrophysical impact

  17. 150 100 50 7Be H2 gas 20 15 10 5 0 7Be(p,p0)7Be cm=128 Solar Physics: Understanding 8B and the solar thermonuclear7Be(p,)8B reaction Measurements of 7Be+p elastic & inelastic scattering have improved our understanding of the 8Be level structure d/d (mb/sr) 7Be(p,p1)7Be* cm=124 First statistically significant direct measurements of the 7Be(p,)8B cross section using a 7Be beam are testing systematic uncertainties in the 7Be(p,)8B cross section Ecm (MeV) 8B 4+ Daresbury Recoil Separator 5+ ionization chamber

  18. “Best studied” deformed proton emitters 141gsHo and 141mHo Excited states in 141Ho from GS+FMA exp ! 7.4(3)ms ~1.7% Both measured properties of 141mHo decay, the decay rate (factor 2-3 too large) and fine structure (factor 5 too small) call for a change in our understanding of the 141mHo (and 141gsHo) wave function • 141Ho is 20 neutrons away from stable 161Ho • Tensor interaction plays a role in proton-rich systems

  19. Vision for the Future…

  20. Radioactive Ion Beam Facilities Timeline 2000 2005 2010 2015 2020 In Flight ISOL Fission+Gas Stopping Beam on target HIE-ISOLDE ISOLDE ISAC-II ISAC-I SPIRAL2 SPIRAL FAIR SIS RIBF RARF NSCL HRIBF CARIBU@ATLAS FRIB

  21. An a electron accelerator with a energy >25 MeV and power in the 50 to 200 kW range makes a remarkably cost-effective high-intensity source of rare isotopes This is an upgrade with a strong neutron-rich physics bias (photo-fission based) Can achieve 1013 f/s baseline with ~10kW deposited in UCx target (60 - 50 kW at 25 - 50 MeV) Requires Ee ≥ 25 MeV + optimized converter:1.5 - 3 Xo (Ee dep.) 3 to 5 times greater than baseline is reasonable expectation This level of yield is competitive with any ISOL facility scheduled to produce n-rich RIBs before FRIB is on line The fact that a 25 MeV facility is feasible increases options Concept supported by HRIBF SPC, and at eRIB07 workshop A low-power e-beam driven facility is being implemented at Orsay Conclusions of extensive e-driver studies

  22. Over 17 units sold, including ISOMEDIX (USA) STUDER (SWITZERLAND) A.E.0.I.( IRAN) ENUSA (SPAIN) ECI (BELGIUM) RISTRON (GERMANY) HOSPAL (ITALY) IBA RhodotronElectron AcceleratorWilling to scale their 10 MeV, 20mA unit (shown) to 25 MeV

  23. Photofission yields • 1013 f/s “easily” achieved • About 20x current HRIBF • But real gain >> 20x 238U(g,f) (p,f) systematics from Tsukada (g,F) from ORNL systematics + Jyväskylä model

  24. RIB production by photofission 1013ph-f/s 10 mA 40 MeV p

  25. Photo-fission yield Post-accelerated

  26. Nuclear Structure Probing the disappearance of shells Spectroscopy & reactions in 132Sn, 78Ni regions Evolution of collective motion We can probe 112Zr and 96Kr regions (not 156Ba) Neutron Skins Structure/reaction studies of the most n-rich species SHE Reactions with 132Sn (~109) and vicinity For Z=112, N=184, reaction mech. Studies with 92,94Sr (106, 107) Nuclear Astrophysics Decay spectroscopy (bn, t) Stockpile Stewardship Surrogate reactions (n transfer, etc.) RISAC Science Drivers & the electron driver Note strong emphasis on n-rich side of stability

  27. Concentrate on 78Ni and 132Sn regions In beam spectroscopy Coulex (B(E2)) Lifetimes Coulex ( Static moments: Q & g) Transfer 1 nucleon: shell structure 2 nucleon: pairing Decay spectroscopy Halflives -delayed neutron spectroscopy Masses Total decay heat Ground and metastable state g-factors (b-nmr) A couple of examples …. Shells and r-process

  28. r-process for nn = 1020, 1023 ,1026neutrons/cm3 Z N F.-K.Thielemann,K.-L.Kratz, P.Möller, et al., AstroPhys. J. 403,1993; Phys. Rev. C67, 2003 82 84 86 88 90 92 94 most n-rich isotope with reported half-life Chart of Nuclei, 7th ed.,August 2006 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se b-decay reach at the eHRIBF As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 “waiting-point“ isotopes at nn=1026 freeze-out

  29. At least three r-process components, at very different neutron densities, are needed to explain observed isobaric abundances (F.K.Thielemann.K.L.Kratz, P.Moeller et al., 1993 - 2006) nn=1020 nn=1023 nn=1026 HRIBF now HRIBF with LeRIBSS eHRIBF with LeRIBSS

  30. Transfer reactions: shell structure of n-rich nuclei Single-particle states around closed shells provide a fundamental shell model test Example: (d,n)-like reactions  neutron s.p. levels RIB Recoils detected in coincidence protons detected in Si-array 132Sn(d,p)133Sn @ HRIBF with the e-driver 3p3/2 Jones et al. 6x104 ions/s Single-particle transfer near 78Ni and 132Sn 2f7/2 3p1/2? 2f5/2 Reactions of interest (d,p) (9Be,8Be) (13C,12C) (3He,d) (3He,) (7Li,8Be) EP (channels) Ex

  31. Accessible at HRIBF Accessible with e-machine Neutron transfer reactions

  32. Science highlights with e-driver upgrade • Will test the evolution of nuclear structure to the extremes of isospin • Will improve our understanding of the origins of the heavy elements Evolution of single-particle structure Transfer reactions at 132Sn & beyond Collective properties in extended neutron radii Coulomb excitation near 96Kr Reaction mechanisms for the formation of superheavy nuclei Decay properties of nuclei at the limits Crucial for understanding the formation of elements from iron to uranium

  33. Science with fission fragment beams is the keystone of our research program and will continue to be An electron-beam based facility can produce intense n-rich beams in a remarkably cost-effective way Such a facility would be competitive world-wide for neutron-rich beams until FRIB-scale facilities are available 1013 photo-fissions/second is a reasonable baseline to work from – 3 to 5 x more is not unreasonable The facility can be implemented largely with commercially available components – (~80% outsourced) Cost containment is critical – cost-effectiveness is a major part of the argument Summary

  34. The End

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