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Decay Studies of Exotic Nuclei with RISING & the GSI Fragment Separator

Decay Studies of Exotic Nuclei with RISING & the GSI Fragment Separator Spokesperson for the Stopped Beam RISING collaboration: P.H.Regan GSI contacts: J.Gerl & H.J.Wollersheim  Part of the ‘Stopped Beam’ RISING experimental campaign at GSI. PARTICIPANTS CENBG Bordeaux, France: B. Blank

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Decay Studies of Exotic Nuclei with RISING & the GSI Fragment Separator

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  1. Decay Studies of Exotic Nuclei with RISING & the GSI Fragment Separator Spokesperson for the Stopped Beam RISING collaboration: P.H.Regan GSI contacts: J.Gerl & H.J.Wollersheim  Part of the ‘Stopped Beam’ RISING experimental campaign at GSI. PARTICIPANTS CENBG Bordeaux, France: B. Blank GSI-Darmstadt, Germany: J.Gerl, H.J.Wollersheim, F.Becker, H.Grawe, M.Gorska, P.Bednarczyk, N.Saitoh, T.Saitoh IKP Koeln, Germany: J. Jolie, P. Reiter, N. Warr, A. Richard, A. Scherillo, N. Warr TU Munchen: R. Krücken, T. Faestermann University of Camerino, Italy: D. Balabanski, K.Gladnishki, IFJ PAN Krakow, Poland: A. Maj, J. Grebosz, M. Kmiecik, K. Mazurek Warsaw University, Poland: M. Pfűtzner Universidad Autonoma de Madrid, Spain: A. Jungclaus Universidad de Santiago de Compostela, Spain: D. Cortina Gil, J. Benlliure, T. Kurtukian Nieto, E. Caserejos IFIC Valencia, Spain: B. Rubio INFN-Legnaro, Italy: A. Gadea, G. deAngelis, J.J. Valiente Dobon, N. Marginean, D. Napoli, INFN-Padova, Italy: E. Farnea, D. Bazzacco, S. Lunardi, R. Marginean University and INFN-Milano: A. Bracco, G. Benzoni, F. Camera, B. Million, O. Wieland, S. Leoni University of Surrey, UK: Zs. Podolyàk, P.H. Regan, P.M. Walker, W. Gelletly, W.N.Catford, Z. Liu, S. Williams University of York, UK: M.A. Bentley, R. Wadsworth University of Brighton, UK: A.M. Bruce University of Manchester, UK: D.M. Cullen, S.J. Freeman University of Liverpool, UK: R.D. Page University of Edinburgh, UK: P. Woods, T. Davinson CLRC Daresbury, UK: J. Simpson, D. Warner Uppsala University, Sweden: H. Mach Lund University, Sweden: D. Rudolph Lawrence Berkeley National Lab, USA: R.M. Clark University of Notre Dame, USA: M. Wiescher, A. Aprahamian Youngstown State University, Ohio, USA: J.J. Carroll Debrecen, Hungary: A. Algora

  2. Use of FRS and RISING gamma-ray spectrometer to study internal structure of extremely exotic nuclei. Relativistic projectile fragmentation to populate Heavy, neutron-rich nuclei (cold fragmentation). N~Z nuclei approaching the proton drip-line. Active, position sensitive, pixellated stopper to correlate implanted ions (mother) with b-decay. Measure g rays (internal structure) from decays of ns-ms isomeric states in original implanted ion, and / or excited states in b-daughter nucleus. Overall Physics Aims and Technical Background

  3. abrasion ablation fragmentation Fragmentation at relativistic energies

  4. 1. N~126 2. 190W - 170Dy 4. 71Kr 3. 128,130Cd 5. 62Ga 6. 50Fe

  5. Fragmentation at relativistic energies Initial population in spin/energy plane reasonably well known from isomer ratio work. Good estimates of isomer population using ABRABLA and (neutron-rich) production cross-section with COFRA • - ion-by-ion identification using FRS. • decay out from the isomers/betas • time correlated with fragments • (flight time through FRS: ~300ns)

  6. In-Flight Technique Using Projectile Fragmentation Production target Central focus, S2 Final focus, S4 primary beam Pb @ 1GeV/u dipole, Br degrader degrader MW=x,y scint catcher scint DE(Z2) scint (veto) Use Fragment Separator to ID individual nuclei. Transport some in isomeric states (TOF~ x00ns). Stop and correlate decays with nuclei id. eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 -> LISE M. Pfützner et al. Phys. Lett. B444 (1998) p32 -> FRS Zs. Podolyàk et al. Phys. Lett. B491 (2000) p225 -> FRS M. Pfützner et al. Phys Rev. C65 (2002) 064604 -> FRS M. Caamano et al., Eur. Phys. J. A23 (2005) p201 -> FRS

  7. M. Pfützner et al., Phys. Rev. C65 (2002) 064604; K. Gladnishki et al., Phys. Rev. C69 (2004) 024617 Higher spins for greater DA.

  8. 208Pb beam at 1 GeV/u showed production of heavy, neutron-rich (A>170-200) high-spin (>35/2 h) isomers. Pfützner et al. Phys Rev. C65 (2002) 064604 High spins (>35/2) populated

  9. 14.3 ns M. Caamano et al., Eur. Phy. J A23 (2005) p201 Stripping the ions of electrons lengthens the apparent isomeric decay half-life by ‘switching off’ conversion electron decay branch

  10. 4p 197Au+9Be 5p Cold fragmentation (protons out) to produce neutron-rich nuclei is well modelled by theoretical estimates.

  11. DE degrader O-O 1-O O-1 O-2 DE MUSIC Charge states in the FRS: A/Q identification Difference between Br1 and Br2 with a degrader and a stripper at S2

  12. Charge states in the MUSICs: Z identification Correlated measurement with two MUSICs with a stripper in between DE Music 1 DE Music 2 DE DE Music 1 DE Music 2

  13. Fragmentation of 1 GeV/u 208Pb, M. Caamano et al., Eur. Phy. J A23 (2005) p201 188Ta fully-stripped H-like 184Lu, H-like fully-stripped

  14. Prompt ‘flash’ can be a limiting problem for fragmentation isomer spectroscopy. Can reduce the effective Ge efficiency factors of 3-4 for close geometry…. but 105 (15 x 7) detectors in RISING will improve this.

  15. degrader beam MW42 MUSIC MUSIC MW41 Sci41 RISING set-up with stopped beams RISING Ge Cluster Array.

  16. 5 at 510, 5 at 900 and 5 at 1290 all at 209.8mm Photopeak efficiency17.2% at 1.3MeV 8 BaF2 detectors (185-220mm)

  17. 5 at 510, 5 at 900 and 5 at 1290 all at 209.8mm Photopeak efficiency17.2% at 1.3MeV 8 BaF2 detectors (185-220mm)

  18. Implantation detector double sided silicon strip detector active area 50x50 mm2 thickness 1 mm 16 strips in x- and y-direction Active stopper = 3 x DSSSD Active area, 15cm x 5 cm

  19. Implantation range • Monoenergetic degrader at S2: • larger implantation surface at S4 • smaller dispersion in the implantation range Achromatic degrader Monoenergetic degrader

  20. charge states Silicium thickness (mm) Implantation range Estimated implanted isotopes for a setting centered on 192W in 1 mm thickness silicon with a monoenergetic degrader at S2

  21. Detector setup for b half lives measurement Active catcher for implantation-decay correlations • Implantation-decay correlations with large background • (half lifes similar to the implantation rate): • implantation-decay time correlation: active catcher • implantation-decay position correlation: granularity • implantation of several ions: thickness and area • energy of the implanted ion and the emitted b 3 double-side silicon-strip detectors - surface 5x5 cm2 - thickness 1 mm - 2 x 16 3.125 mm strips - manufactured by MICRON

  22. 3 x 16 x 16 = 3 x 256 = 768 total pixels. Assume upper limit for b-half-life of ~30 seconds Each pixel hit every 5 half-lives (150 secs) Max. rate of ~768/150 = 5 per sec ( = 50 per 10s spill). Rate increases directly with decreasing half-life (e.g., T1/2 = 10 seconds -> 150 per 10 s spill cycle) Dual gain pre-amps on DSSSD to get energies of implanted ion and b-particle All events time stamped with MHz clock. Count Rate Limitations with Active Stopper

  23. MUSIC 1 MUSIC 2 SC42 SC4 MUSIC 3 SC43 Implantation procedure Setting centered on 186Lu Produced Implanted Sc42 Sc43

  24. The GSI FRS γ-Ray Spectroscopy Campaign S210 (2001) ü ü ü

  25. RISING: Stopped Beam Campaign

  26. STOPPED BEAM CAMPAIGN - A Proposal A:1 (S312) b-Decay Lifetimes, b--Delayed Spectroscopy Studies and Collective Evolution ‘South’ of 208Pb J. Benlliure, P.H. Regan et al., Universidade de Santiago de Compostela, Spain Department of Physics, University of Surrey, Guildford, GU2 7XH, UK IKP, University of Cologne, 50937 Cologne, Germany Planckstrasse 1, GSI, Germany TU Muenchen, Germany Warsaw University, Poland Uppsala University, Sweden Dept. of Physics, University of Liverpool, UK Dept. of Physics and Astronomy, University of Manchester, UK CLRC Daresbury Laboratory, Cheshire, UK University of Camerino, Italy Universidad Autonoma de Madrid, Spain

  27. STOPPED BEAM CAMPAIGN - A Proposal A:2 (S313) Nuclear Dynamical Symmetries and Shape Evolution in K-isomeric Nuclei from 190W to the 170Dy Valence Maximum. P.H. Regan, J. Benllliure et al., Department of Physics, University of Surrey, Guildford, GU2 7XH, UK University of Santiago de Compostela, Spain IKP, University of Cologne, 50937 Cologne, Germany Planckstrasse 1, GSI, Germany Warsaw University, Poland Uppsala University, Sweden CLRC Daresbury Laboratory, Cheshire, UK  University of Camerino, Italy University of Manchester, UK Youngstown State University, Ohio, USA  IJF, PAN Krakow, Poland

  28. Nilsson scheme:Quadrupole deformed 3-D HO. where hw -> hwx+hwy+hwz axial symmetry means wx=wy Spherical, harmon. oscilator H = hw+al.l+bl.s, quantum numbers jp, mj > prolate b2 quantum numbers [N,nx,L]Wp x High-W (DAL) orbit z h9/2 (10) Wp x 82 h11/2 (12) Mid-W (FAL) z d3/2 (4) s1/2 (2) Wp d5/2 (6) x g7/2 Low-W, (RAL) (8) 50 z g9/2 (10) Effect of Nuclear Deformation on (K) isomers Kp= sum of individual Wpvalues.

  29. Expect to find K-isomers in regions where high-K orbitals are at the Fermi surface. Also need large, axially symmetric deformation (b2>0.2, g~0o) Conditions fulfilled at A~170-190 rare-earth reg. 82 50 126 High-W single particle orbitals from eg. i13/2 neutrons couple together to give energetically favoured states with high-K (=SWi). 82

  30. low-K mid-K high-K j K Search for long (>100ms) K-isomers in neutron-rich(ish) A~180 nuclei. Walker and Dracoulis Hyp. Int. 135 83 (2001) (Stable beam) fusion limit makes high-K in neutron rich hard to synthesise Alaga, Alder, Bohr and Mottelson, Mat. Fys. Medd. 29 no 9 (1955)

  31. Podolyak et al., Phys. Lett. 491B (2000) 225; Caamano et al., EPJ A23 (2005) 201 Discontinuity (change of structure) observed for 190W following GSI isomer (Kp=10-) spectroscopy.

  32. E(2+) is signature of deformation. Possible shape change identified from 190W data point (N=116). Proposal to identify first 2+ state in 192W (N=118) 188,190Hf (N=116,118) 186,188Yb (N=116,118) Decays from Ip=10- isomers and/or b- decay of 192Ta 188,190Lu and 186,188Tm t1/2 ~1-5 secs

  33. Constrained HF calculations (Stevenson) suggest prolate-oblate shape change/competition at N=116 isotones, 188Hf, 190W, etc. Physics interpretation consistent with O(6) ‘critical point’ in extended ‘Casten triangle’ at phase transition between prolate and oblate axially symmetric shapes. See Jolie and Linnemann, Phys. Rev. C68 (2003) 031301(R)

  34. 170Dy, double mid-shell, nature’s purest K-isomer ? P.H. Regan et al. Phys. Rev. C65 (2002) 037302 Kp=6+ isomer Kp=0+ band Reduced hindrance correlated with Np.Nn…max. at 170Dy...

  35. Apparent underlying SU(3) dynamical symmetry for N=104. (see Casten et al., Phys. Rev. C31 (1984) R1991) Is 170Dy nature’s best SU(3) nucleus too ? 168Tb->168Dy, T1/2=8 s Asai et al., Phys. Rev. C59 (1999) 3060

  36. Primary 198Pt beam @ 1GeV/u, intensity of 109 particles per spill, 10 second spill cycle. 2.5 g/cm2 thick Be target, 5.1g/cm2 Al. degrader at S2, plus a 108mg/cm2 Niobium stripper. Cross-section estimates from the COFRA.Estimated values for transmission per eight hour shift are: Setting 1: Centred on 191W190W 1x107191W 0.4x107192W 0.4 x107 Setting 2: Centred on 187Hf187Hf 3.7x105 188Hf 9x104 189Hf 1x104 Setting 3: Centred on 185Yb184Yb 2x104185Yb 6x103186Yb 240 20% g-ray efficiency for 662 keV, (~50%) prompt-flash, isom. ratio (~5%), Yield estimates for observed photopeak g rays per 8 hour shift of 190W 250,000 ; 192W 100,000 ; 188Hf 2,250 ; 184Yb 500 ; 186Yb 6 Setting 4: Centred on 170Dy170Dy 1.4x105170Tb 4,500 168Tb 4.9x104 Assuming g-ray (0.2) and b-detection (0.5) efficiency for decays of 170Tb gives 450 photopeak g rays from the decay of the first 2+ state in 170Dy per shift. Setting 1: 3 shifts (1 day) ; Setting 2: 3 shifts (1 days) Setting 3: 6 shifts (2 days) ; Setting 4: 6 shifts (2 days) 2 days (6 shifts) primary beam tuning and particle id. calibrations, 191W setting: Total beam request of 24 shifts (8 days). 

  37. STOPPED BEAM CAMPAIGN - A Proposal A:3 (S305) Search for the 8+ (g9/2)-2 isomer in N=82 130Cd populated via the 6 proton knockout channel in the fragmentation of 136Xe A. Jungclaus et al., Universidad Autónoma de Madrid, Spain Institute of Nuclear Research, Debrecen, Hungary Universidad de Santiago de Compostela, Spain GSI Darmstadt, Germany Uppsala University, Sweden University of Surrey, UK Universität zu Köln, Germany University Warsow, Poland IFIC Valencia, Spain Lund University, Sweden

  38. Search for the 8+ (g9/2)-2 isomer in N=82 130Cd populated via the 6 proton knockout channel in the fragmentation of 136Xe Why study 130Cd ? 132Sn astrophysical reasons: 130Cd is the most important waiting-point nucleus before the r-process breakout of the N=82 shell relation between N=82 shell closure and the A~130 peak of the solar r-process abundance distribution Z=50 130Cd r-process path N=82

  39. Sn Cd Te Pd Kautsch et al., EPJ A9 (2000) 201 -decay @ ISOLDE nuclear structure reasons: unexpected behaviour of the 2+ excitation energies of even Cd isotopes towards the N=82 shell closure (change of curva- ture starts already at 124Cd) there is a series of other nuclear structure puzzles in the 132Sn region Is this behaviour really a “signature of a weakening of the N=82 shell structure already one proton-pair below 132Sn” as suggested by the authors of the experimental study ?

  40. Is there an alternative explanation ? mean-field after angular momentum projection 208Pb 130Cd 132Sn 128Cd 126Cd 132Sn curve much broader than that for 208Pb fluctuations in 2 much more important in 132Sn indicating that a higher degree of collec- tivity remains in 132Sn as compared to 208Pb after angular momentum projection, 126Cd and 128Cd show deep prolate minima already at I=2ħ Does quadrupole collectivity persists close to N=82 in the chain of Cd isotopes ? (Remember: 32Mg is spherical at mean field level, but deformed after projection !) constrained HFB+AMP with Gogny force, J.L. Egido

  41. Sn Cd Te Pd A=126 A=128 -decay study of heavy Cd isotopes at ISOLDE “… has to be considered speculative …” “… close to the present limit that can be achieved with RILIS and GPS-ISOLDE.” In general: Problems due to beam intensity and dominating In and Cs isobaric activities ! Can probably not be done better at ISOLDE at the moment ! Kautsch et al., Eur. Phys. J. A9 (2000) 201

  42. Gd Sm N=Z Nd Z Ce Ba Xe 132Sn 100Sn Te 50 Cd 82 Pd 80 Ru 76 78 74 Mo 72 50 68 70 Sr N 58 60 62 Ge Zn 54 56 Ni 28 30 32 34 36 38 40 42 44 46 48 52 (g9/2)-2 (d5/2 g7/2)2 (g9/2)-2 (f7/2)2 (g7/2)2 (h11/2)-2 480 ns 1.6 s 10+ 8+ 8+ 1.0 s 6+ 6+ 6+ 4+ 4+ 4+ ? 165 ns 6+ 4+ 2+ 80 ns 2+ 6+ 2+ 2+ 4+ 2+ 0+ 0+ 0+ 0+ 0+ 0+ 98Cd 102Sn 130Cd 134Sn 134Te 130Sn Study of 8+ isomer decay in 130Cd (and 128Cd) 8+ isomer with (g9/2)-2con- figuration expected in 130Cd in analogy to the one in 98Cd • Advantage compared to -decay: • possible observation of whole se- • quence up to the 8+ state • lifetime of the isomer itself contains • valuable information already searched for without success at LOHENGRIN and FRS (Mineva, Hellström et al.)

  43. Production of 130Cd @ FRS implantation rate at the focal plane: I [sec-1] =  [cm2] · d[g/cm2]· A-1[mol/g]· [sec-1]· Ttot· NA[mol-1] cold fragmentation of 136Xe for Be target 238U fission 0.1 b 0.154 nb cross section  calc. ! measured ! 1 g/cm2 2.5 g/cm2 target thickness d 109/spill (15s) 5·109/spill (5s) primary beam current  3.5% 95% total transmission 0.9 (1300) 1.4 (2000) implanted 130Cd/min(d) Mineva et al.: =2·107 sec-1 in total 700 implanted 130Cd measured  easier beam easier exp.

  44. Transmission simulations with the Lieschen code 130Cd setting 131In setting Z Z 132Sn 130In 129In 127Cd 130Cd N N known isomers in 127Cd and 130In will be observed at the same time in the setting optimized for 130Cd this setting could be used for a quick calibration using the known isomers in the strongly populated nuclei 132Sn and 129In

  45. STOPPED BEAM CAMPAIGN - A • Proposal A:4 (S314) • Exotic Beta decays near the proton-drip line: • study of the beta decay of 70,71Kr. • A. Algora, B. Rubio, W. Gelletly et al., • Institute of Nuclear Research, Debrecen, Hungary • IFIC, CSIC, Valencia, Spain • University of Surrey, Guildford, UK • University Santiago de Compostela, Santiago, Spain • Osaka University, Osaka, Japan • Universidad Autonoma de Madrid, Madrid, Spain • CIEMAT, Madrid, Spain • GSI, Darmstadt, Germany • LNL, Legnaro, Italy

  46. 71Kr case: Motivations • Study of mirror T=1/2 pairs • Identification of IAS of 71Kr g.s. (not known) • N~Z region around Z=36-38: shape effects, shape coexistence, shape transitions, isospin symmetry • Determination of the ground deformation of 71Kr Exotic decays near the proton-drip line: study of the beta decay of 70,71Kr

  47. 71Kr case II Ref. Oinonen et al PRC 52 (1997) 745

  48. Motivation: Search for states populated in the beta decay of 70Kr, which may indicate the existence of the proton-neutron condensate Background: Validity of the IBM-4 classification scheme in light nuclei (18Ne18F, P. Halse, et al. NPA 417 (1984) 301) Existence of some examples in medium-heavy and heavy nuclei that can be explained using this scheme. Transitions with small log ft, that can not be explained because of large hindrance factors in fermion transitions but can be explained assuming boson transitions. (130Sn131Sb, Iachello et. al). Necessity to study systems in the vicinity of the N~Z line 70Kr case I

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