Fritz Peter Heßberger

Transcription

1 Fritz Peter Heßberger GSI Helmholtzzentrum für Schwerionenforschung mbh, D Darmstadt, Germany Helmholtz Institut Mainz D Mainz, Germany International Conference Beyond 2010 Cape Town, South Africa February 2010 Version

2 Outline of the talk Physical Motivation Experimental Set-ups at GSI GSI Experiments on Search for SHE GSI Experiments on Nuclear Structure of SHE New Accelerator Project New Separator Projects New detection set-ups and techniques Conclusions Collaborations

3 Predictions of Superheavy Elements Macroscopic Microscopic Calculations (164) (164) H. Meldner Arkiv fys. 36,593 (1967)

4 Skyrme-Hartree-Fock (SHF) and Relativistic Mean Field (RMF) Approaches Self-consistent Skyrme-Hartree-Fock (SHF) calculation and Relativistic Mean Field (RMF) calculations, using different parametrizations. SHF: SkP, SkI3, SLy6, SkI4 and RMF: NL3, NL-Z2. Results different for different parametrizations, also different from macroscopic-microscopic calculations SkP predicts proton shell Z=126, other SHF param. rather Z=120, SkI4 shows also stromg shell effects at Z=114; SHF predict neutron shell essentially at N=184, partly strong shell effects also at N=172 RMF predict proton shell at Z=120 and strong neutron shell rather at N=172. Where are the shells really??? From: M.Bender et al. Phys. Lett. B 515, 42 (2001)

5 Excerpt from the Charts of Nuclei Regions of Research Z Bh Hs Mt Ds 112 Rg 270 Hs N

6 48 Ca E lab = 220 MeV Production of Superheavy Elements 209 Bi 257 Lr E * = 22 MeV n ye Lr (<0.1%) 'prompt disruption' (>99.9 %) n xγ Production of SHE in complete fusion reactions Cold fusion: Pb, Bi Targets, medium heavy projectiles (e.g. 48 Ca, 54 Cr, 64 Ni), low excit. energy E*(B fus ) < 20 MeV, 1n (2n), high dyn. fusion hindrance Hot fusion: Actinide targets ( 244 Pu, 248 Cm), projectile 48 Ca (mostly so far); high excit. energy, E*(B fus ) > 30 MeV, 3n, 4n, (5n), lower dyn. fusion hindrance, more neutron rich nuclei, closer to N=184 F.P.Heßberger Hot Fusion fusion cross-section 209 Bi( 48 Ca,xn) 257-x Lr Cold Fusion σ / nb Lr (1n) 255 Lr (2n) 254 Lr (3n) 253 Lr (4n) 10 0 Yu. Oganessian, J. Phys. G 34, 165 (2007) F.P.Heßberger, EPJ D45, 33 (2007) E* / MeV

7 Production of Superheavy Elements σ / pbarn ,1 (4n) 'cold' fusion (Pb,Bi-targets) 34 S + actinide targets 48 Ca + actinide targets (3n) 48 Ca + actinide targets (4n) 22 Ne, 30 Si U (5n) 50 Ti Pb 54 Cr Pb 58 Fe Pb 64 Ni Pb 70 Zn Pb decrease of E* for maxumim of 1n channel 0, Z ER konferenzen/tours/quersschn Ca Pu

8 Schematic Experimental Set-up for SHE - Research sf sf

9 Velocity separator SHIP SHIP Separation time: 1 2 μs Transmission: % Background: Hz Det. E. resolution: kev Det. Pos. resolution: 150 μm Dead time: 25 μs Mastertitelformat bearbeiten

10 Gas filled Separator TASCA Modes of Operation: Æ High Transmission Mode (HTM); DQhQv focussing; ε = 57±5 % for 253No (48Ca + 207Pb) Beam spot size: 120x40 mm2 Æ Small Image Mode (SIM); DQvQh focussing; ε = 35±6 % for 253No (48Ca + 207Pb) Beam spot size: 30x30 mm2

11 Synthesis of by the reaction 48 Ca U σ = pb σ = pb New result: b sf ( ) = 50±20 %

12 Synthesis of Element 114 by 48 Ca Pu 12 decay chains σ 5 pb E* 41 MeV 5 decay chains σ 1.7 pb E* 41 MeV New results at TASCA: α-decay branch in 281 Ds new isotope 277 Hs

13 54 Cr Cm:σ 25 fb (4n) 58 Fe Pu: σ 5 fb (4n) 64 Ni U: σ 4 fb (3n) Towards Element 120 First attempt at SHIP: 64 Ni U (S.Hofmann et al. GSI Sci. Rep. 2008, 131) 50 Ti Cf: σ 50fb (4n) 50 Ti Cf: σ 250 fb (4n) Beam dose: 2.11 x (116 days) : σ < 90 fb B f (mac.-mic) 7 MeV ( (N=180)) (p-shell at Z = 114) B f (SLy6,SKP...) (10-12) MeV ( (N=180)) (p-shell at Z 120) Cross-section enhancement expected at higher B f Problem: fusion probability!! V. Zagrebaev, W. Greiner PR C 78, (2008) Next step: 54 Cr Cm (in preparation) Alternatively: 50 Ti Cf, 252 Cf σ(3n) 10 pb σ(4n) 1 pb σ(3n) σ (3n) 10 fb σ (4n) 1 fb σ (4n) fb A.K.Nasirov et al. PR C79, (2009)

14 Nuclear Structure Investigations 184 j15/2 7/2+[624] 152 9/2-[734] g9/ /2-[521] f7/2 100 i13/2 h9/ /2-[514] f5/2 d5/ /2-[521] 7/2+[633] 1/2+[631] 82 Nilsson Diagrams for Neutron (left) and proton (right) single particle levels

15 Prompt alpha-gamma spectroscopy 207 Pb( 48 Ca,2n) 253 No : σ 900 nb h; α-decays collected in 96 h irrad. time counts 12k 11k 10k 9k 8k 7k 6k 5k 4k 3k 2k 1k K-x-rays (Fm) 151 kev 222 kev 280 kev counts kev 58 kev 128 kev 209 kev E γ / kev 297 kev 670 kev E γ / kev hess/konferenzen/tan_0907/no253_r239_r260 F.P.Heßberger,

16 Comparison of decay properties of N=151 isotones 251 Fm: α Cf, σ 10 mb, b α = 1.8 % 253 No: 207 Pb( 48 Ca,2n) 253 No, σ 0.9 µb, b α 80 % 255 Rf: 207 Pb( 50 Ti,2n) 255 Rf σ 10 nb, b α 50% 9/2 - [734] 251 Fm 9/2 - [734] 253 No 9/2 - [734] 255 Rf 800 7/2 - [743] α (6639, 0.006) α (6834, 0.87) 7/2 - [743] α (6929, 0.018) α (7620, 0.001) E * / kev /2 - [734] 7/2 + 5/2 + [622] α (8004, 0.96) α (8078, 0.04) α (8730, >0.9) E1 (0.24) E1 (0.57) E1 (0.19) 9/2 - [734] /2 + M1 5/2 + [622] 11/2 + E1 (0.23) E1 (0.63) 9/2 + 9/2 + 9/2 + 7/2 + [624] 7/2 + [624] 7/2 + [624] 247 Cf E1 (0.14) 249 Fm M1 9/2 - [734] E1 (0.45) E1 (0.55) 251 No I. Ahmad et al. PR C 8, 737 (1973) F.P. Heßberger EPJ D 45, 33 (2007) and this work F.P.Heßberger et al. EPJ A 30, 561 (2006)

17 Systematics of low lying Nilsson levels in N = 149 isotones Theory (A.Parkhomenko, A.Sobiczewski, Act. Phy. Pol. B 36, 3115 (2005)) 600 7/2 - [743] Experiment 1/2 + [631] 500 7/2 - [743] 500 E * / kev E * / kev /2 - [734] 1/2 + [631] 5/2 + [622] /2 + [622] 9/2 - [734] s 0 7/2 + [624] 243 Pu 245 Cm 247 Cf 249 Fm 251 No 253 Rf 255 Sg 0 7/2 + [624] 243 Pu 245 Pu 247 Cf 249 Fm 251 No

18 Decay of K-Isomeric states in 254 No m2 No (198 ms) 198 ± 13 μs (16 -,16 + ) 2917 ± 3 kev b sf 1.2x10-4 counts / kev counts / kev (x0.5) , 168, , 159 (214) m1 No (275 ms) E γ / kev F.P.Heßberger et al. EPJ A 43, 55 (2010) (x0.5) (145) 133 (123) 111 K= No (256) 1295 ± 2 kev 275 ± 7 ms π9/2 + [624] x π7/2 - [514] b sf =(2.0±1.2)x10-4 b α 1x K= (M1) 943 (M1) 987 kev π1/2 - [521] x π7/2 - [514]

19 Decay of a K-Isomeric state in 252 No Counts Pb( 48 Ca,2n) 252m No 107 (4+ --> 2+) (line dublett) K α1,2 (+ 123?) (6+ --> 4+) 224 (8+ --> 6+) No (25) 1229 (7-) (6-) 1073 (5-) (4-) 966 (3-) 929 (2-) 100 ms 1254 kev (8 _ ) 50 No252iso F.P.Heßberger E γ / kev No252_KIsomer_ F.P.Heßberger ,5-,8-9/2+ 7/2-1/2-7/2+ 3/2-1/ /2+ 1/2+ 7/2+ 11/2-9/2-7/2+ 5/2+ Z N B. Sulignano et al. EPJ A 33, 327 (2007) 8-

20 K-isomers in N=150 isotones E* / kev quasi p 2-quasi n 8+ (7/2-,9/2-) 4+ (1/2+,7/2+) 7- (5/2+,9/2-) 4- (3/2-,5/2+) exp. 8- T 1/2 =? 8- (7/2+,9/2-) 3- (1/2-,5/2+) 6+ (5/2+,7/2+) 5- (3/2-,7/2+) 2+ (1/2-,3/2-) 4+ (1/2-,7/2-) 7- (7/2+,7/2-) 1.8 s 4- (1/2-,7/2+) 4+ (1/2-,7/2-) 0.1 s Decay schemes of 252 No and 250 Fm similar; but different to that of 254 No!! Suggests similar structure of isomers in 252 No and 250 Fm. Supported by calculatuions; lowest 2quasi particle configuration predicted as 2quasi neutron state with I π = 8 -. Common trend in N=150 isotones? next heavier candidate is 254 Rf 246 Cm 248 Cf 250 Fm 252 No calc. J.-P. Delaroche et al. Nucl. Phys. A 771, 103 (2006)

21 Mean time of flight / μs No 2+ SHIPTRAP Excitation frequency / Hz Stopping Cell 1 2 Extraction RFQ 1. deceleration 2. cooling 3. accumulation 4. purifucation 5. storage 6. detection fusion products from SHIP Buncher 3 Purification Trap Measurement Trap 6 5 Detector Downstream Experiments Plans: 254,255,256 Lr,... towards doubly magic 270 Hs, trap assisted spectroscopy 4 7 Tesla Solenoid 5 6 Masses Measured 252,253,254 No (M.Block et al. accepted for publication in Nature) 255 Lr (first resonance) (M. Dworschak, PHD)

22 7.5 AMeV cw LINAC for the GSI SHE Program Proposal submitted September 2009 (W. Barth, GSI) (not yet approved) Cooperation: GSI Darmstadt, Helmholtz Institute Mainz, Inst. Applied Phys. Goethe Universität Frankfurt Main Features: ( new 28 MHZ ECR source, in progress) ( new RFQ, in commissioning) energy range AMEV 100% duty cycle (presently 25%) intensity increase (> x10) improved beam quality Upgrade presently in progress 28 GHz ECR source + High Charge Injector (RFQ, IH)

23 New Separators Project: Separator for Transfer Reaction Products Inelastic Reaction Isotope Separator for Heavy Elements (IRIS) (J. Dvorak, C.E. Düllmann, M. Schädel) Brainstorming Workshop, March 1st, 2010 Replacement of SHIP, in operation since 1976 (under consideration) SuperSHIP

24 New Detector Set-up - TASISpec Configuration of TASISpec (TASCA in Small Image Mode Spectroscopy) Double sided Si-strip detector (DSSSD); implantation detector, 32x32 strips, active area 58 mm x 58 mm; 0.31 mm thickn. Box of 4 single sided strip detectors (SSSSD) 60 mm x 60 mm active aream 1.0 mm thickn. 1 seven-crystal Ge - Cluster detector (behind implantation detector) 4 four-crystal Ge-Clover detectors expected γ-efficiency 40 % at 200 kev L.L. Andersson et al., GSI Scientific Report 2008, 142 and in preparation to be submitted to NIM

25 TRAP assisted spectroscopy First Commissioning Experiment in September 2009: 170 Er( 48 Ca,5n) 213 Ra Main features: Clean samples, mass separated (no admixtures with isotones) Avoid energy summing of α-particles with conversion electrones D. Rudolph et al. GSI Scientific Report 2009, in press

26 Summary and Outlook Hot Fusion Reactions successfully applied at SHIP ( 48 Ca U *) and TASCA ( 48 Ca Pu *); Dubna chains were reproduced and new decay data obtained Next steps at SHIP: 48 Ca Cm (planned June/ July 2010) Medium range plans: 48 Ca Am * (exc. function), 54 Cr Cm * Further steps: Element 114 chemistry at TASCA ( 48 Ca Pu); depending on availability of beam and targets, 50 Ti Bk *, 50 Ti Cf * Extension of α -γ- (α CE)-decay spectroscopy into the region Z > 106 and towards nuclei around the deformed shells at Z = 108, N = 162 challenge: identification of atomic numbers of SHE via K X-rays detailed investigation of K isomers ( 253 No in scheduled April 2010 at TASCA, 270 Ds scheduled in April/May at SHIP); search for new K isomers around Z = 108, N = 162 precise mass measurements of ground-state and isomeric states in nuclei Z > 100 at SHIPTRAP next step: 255 Lr and 255m Lr (E* 50 kev) scheduled in April 2010 Explore possibilities of trap-assisted spectroscopy in the region of SHE New technical projects: accelerator, separators, detector systems, target developments.... On and on but the road is never ending, at least we know, we re on our way (from On and on by Fiddler s Green)

27 Collaborations SHIP Spokesmen: S.Hofmann, GSI (SHE synthesis) F.P. Heßberger, GSI, Helmholtz Institut Mainz (SHE spectroscopy) GSI, Comenius University Bratislava (Slovakia), FLNR - JINR Dubna (Russia), Univ. Liverpool (UK), Univ. Jväskylä (Finland), JAEA Tokai (Japan), IMP Lanzhou (China), Johannes-Gutenberg Universität Mainz Germany), Helmholtz Institut Mainz (Germany), LLNL Livermore (USA), University of Warsaw (Poland), Goethe Universität Frankfurt (Germany) SHIPTRAP Spokesman: M. Block, GSI GSI, MPI Heidelberg (Germany), Ernst-Moritz-Arndt Universität Greifswald (Germany), Justus- Liebig Universität Gießen (Germany), Johannes-Gutenberg Universtät Mainz (Germany), St. Petersburg Nucl. Phys. Inst. Gatchina (Russia), FLNR-JINR Dubna (Russia), University of Granada (Spain), Ludwig-Maximilians Universität München (Germany), Helmholtz Institut Mainz (Germany), TU Darmstadt (Germany), University of Lund (Sweden), Goethe Universität Frankfurt (Germany) TASCA Spokesman: M. Schädel, GSI GSI, TU München (Germany), Johannes-Gutenberg Universität Mainz (Germany), PSI Villigen (Switzerland), Univ. of Bern (Switzerland), Univ. of Jyväskylä (Finland), LBNL Berkeley (USA), Univ. of California Berkeley (USA), Univ. of Oslo (Norway), Univ. of Lund (Sweden), Univ. of Liverpool (UK), IMP Lanzhou (China), Saha Inst. of Nucl. Phys. Kolkata (India), Helmholtz Institut Mainz (Germany)

28 TASISpec Spokesman: D. Rudolph (Univ. of Lund) Collaborations GSI, Univ. of Lund (Sweden), Univ. of Liverpool (UK), Johannes-Gutenberg Universität Mainz (Germany), Universidad Nacional de Colombia Bogota (Colombia), PSI Villigen (Switzerland), Univ. of Bern (Switzerland), TU München (Germany), Univ. of Oslo (Norway), Helmholtz Institut Mainz (Germany) EL 114 Physics Spokesman: Ch. E. Düllmann (GSI, Univ. Mainz, Helmholtz Institut Mainz) GSI, TU München (Germany), Johannes-Gutenberg Universität Mainz (Germany), Helmholtz Institut Mainz (Germany), Univ. of Liverpool (UK), LBNL Berkeley (USA), Univ. of California Berkeley (USA), Saha Inst. of Nucl. Phys. Kolkata (India), Univ. of Oslo (Norway), Univ. of Lund (Sweden), Univ. of Jyväskylä (Finland), ITE Warsaw (Poland), PSI Villigen (Switzerland), Univ. of Bern (switzerland) EL 114 Chemistry Spokesman: A. Yakushev (TU München) GSI, TU München (Germany), Johannes-Gutenberg Universität Mainz (Germany), Helnholtz Institut Mainz (Germany), JAEA Tokai (Japan), Univ. of Oslo (Norway), Saha Inst. of Nucl. Phys. Kolkata (India), PSI Villigen (Switzerland), Univ. of Bern (Switzerland)