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Sophie Heinz GSI Helmholtzzentrum and Justus-Liebig-Universität Gießen

Fusion and Transfer Reactions in Heavy Collision Systems with Stable and Radioactive Beams. Sophie Heinz GSI Helmholtzzentrum and Justus-Liebig-Universität Gießen. 48 Ca + X. discovered ar GSI - SHIP. discovered at GSI - SHIP. The Heaviest Known Nuclei. B p = 0. B p = 0.

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Sophie Heinz GSI Helmholtzzentrum and Justus-Liebig-Universität Gießen

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  1. Fusion and Transfer Reactions in Heavy Collision Systems with Stable and Radioactive Beams Sophie Heinz GSI Helmholtzzentrum and Justus-Liebig-Universität Gießen

  2. 48Ca + X discovered ar GSI - SHIP discovered at GSI - SHIP The Heaviest Known Nuclei Bp = 0 Bp = 0 X + Pb,Bi valley of β-stability valley of β-stability

  3. V fission barrier Bf ES EC deformation What is a „superheavy“ nucleus ? Binding energy of a nucleus in the liquid drop model (Weizsäcker formula): Coulomb- energy EC Surface energy ES Condensation energy Asymmetry energy Superheavy nuclei: Bf = 0 for Z2 / A > 50 → Z > 100

  4. Superheavy Nuclei: Bfission = Eshell + Epair Fission Barriers of Superheavy Nuclei LD 25098152 LD + shell Shell correction energies in the macroscopic-microscopic model 268106162 Potential energy / MeV 298114184 Quadrupole deformation β2

  5. Where are the next shell closures? Macroscopic-microscopic models Relativistic mean field models 114 114 184 120 120 K. Rutz, W. Greiner et al., 1997 P. Möller, 1995 126 114 Skyrme-Hartree-Fock 126 108 A. Sobiczewski et al., 1995 S. Cwiok et al., 1998

  6. „Cold“ and „Hot“ Fusion Reactions Synthesis of Superheavy Nuclei in Fusion Reactions Cold Fusion→ doubly magic target nuclei: Pb, Bi; E*(CN) = 10 – 20 MeV; evaporation of 1 – 2 neutrons; up to now successful for Z ≤ 113 Hot Fusion→ actinide targets (U, Cm, …) and 48Ca projectiles; E*(CN) = 30 – 40 MeV; evaporation of 3 – 4 neutrons; up to now successful for Z ≤ 118

  7. The Fusion Process in Heavy Systems Nuclear Molecule FUSION Compound Nucleus (CN) TRANSFER, QUASI-FISSION FUSION-FISSION Fission Fragments Evaporation Residue (ER) ER cross-section:

  8. Evaporation Residue Cross-sections Evaporation Residue Cross-sections for Cold and Hot Fusion Reactions Cold fusion (X + Pb, Bi) Hotfusion (48Ca + X) 1 pb corresponds to 1 nucleus per week

  9. Z=116 1 29 ms 2 406 ms 3 6.3 s 49 s sf The Velocity Filter SHIP at GSI Separation + Single Event Identification 100 / s „stop detector" v ~ E/B Δv/v = 0.1 single isotope identification via alpha decays 5 · 1012 / s SHIP: G. Münzenberg Detector: S. Hofmann

  10. σ(293116)/pb σ(292116)/pb +2.1 +2.7 0.9 3.4 - 0.7 -1.6 +1.7 +2.5 1.1 3.3 - 0.7 -1.4 Synthesis of superheavy nuclei at SHIP The reaction 48Ca + 248Cm → 296116* (2010) 4 chains 1 chain 1 chain agree well with earlier data from Dubna observation of an α-branch in 281Ds SHIP S. Hofmann et al., EPJ A 48: 62 Dubna S. Heinz et al., EPJ A 48: 32

  11. Study of Transfer Reactions at SHIP ► Transfer reactions as a means to proudce new neutron-rich (super-)heavy isotopes ► Transfer reactions as first step to fusion 114 184 N-rich superheavy nuclei not reachable in fusion reactions 82 126 N-rich nuclei at N = 126 presently produced in fragmentation reactions

  12. ? ? 92 150 90 88 86 146 142 84 138 82 134 A X Z 80 130 β– 78 126 transfer products observed at SHIP A Y Z+1 Study of Transfer Reactions at SHIP 48Ca + 238U at 4.90 MeV/u → population of n-rich isotopes Isotope ID via α- or gamma decays

  13. Study of Transfer Reactions at SHIP 64Ni + 207Pb → Study of the capture process excitation functions of cold fusion reactions with Pb targets Transfer Transfer Fusion

  14. VNN 232Th + 250Cf U(r,Z,N,L) / MeV R RDNS A1–A2/(A1+A2) r / fm Study of quasi-fission and fusion-fission nucleus-nucleus potential potential energy surface → potential energy landscape determines the preferred evolution paths of the nuclear system

  15. E* = 56 MeV E* = 46 MeV E* = 35 MeV E* = 40 MeV TKE / MeV yield / rel. units mass number Study of quasi-fission and fusion-fission 36S + 238U → 274Hs (Z = 108) courtesy: Y. Itkis et al. → experiments in Dubna, JYFL, … (E. Kozulin et al.) → since 2012 also at GSI (E. Kozulin, S. Heinz et al.) CORSET setup

  16. TOF (MCP detectors) Si stop detector 0.5 – 1 m rotatable The CORSET Spectrometer TOF detector Si detector ΔΩ≈ 50 msr ▪ time resolution: < 150 ps (ΔTOF/TOF ≈ 2 %) ▪ atomic mass from TOF and E (≥ 3 units for very heavy nuclei)

  17. The CORSET Spectrometer CORSET setup at GSI 1 m

  18. Study of other Techniques for Isotope ID Isobaric Identification through precision mass measurements Penningtrap • mass selective • T1/2 > 100 ms • m/Δm > 106 - 107 stopping cell Time-of-Flight spectrometer • broad-band • T1/2 > 10 ms • m/Δm > 105 (T. Dickel, W. Plaß et al., JLU Gießen)

  19. 10-2 mbar 10-4 mbar Injection Trap System Differential Pumping Section 10-6 mbar Time-of-Flight Analyzer Gate Detectors Kinetic Energy 750 eV Ion Gate Isochronous SEM 10-8 mbar Post-Analyzer Reflector The MR-TOF-MS ion catcher (cryogenic) mass filter buncher MR-TOF-MS W. Plass, T. Dickel et al., Univ. Gießen and GSI

  20. Pb, Bi targets actinide targets radioactive beams Fusion Reactions with RIBs → access to neutron-rich superheavy nuclei but: present beam intensities are too low

  21. Required Beam Intensities Required beam intensities to obtain 10 events per day at the given cross-section 500 μg / cm2 targets transfer, quasi-fission, fusion-fission fusion Z ≥ 102 requires separator

  22. Production of new n-rich isotopes in deep inelastic transfer reactions Possible Experiments with RIBs Study of transfer, quasi-fission and fusion-fission in very heavy systems Study of reaction cross-sections as function of the projectile neutron number Required beam intensities: > 107 / s Required beam energies: ≥ 4 MeV / u

  23. Summary ►We perform experiments in the region of the heaviest nuclei: ● Synthesis of superheavy nuclei in fusion reactions ● Study of related processes like capture, quasi-fisison, fusion-fission etc. ● Investigation of different reactions to produce new heavy isotopes ► Experimental setups: ● Separators for reactions with very low cross-sections: σ < 1 μb ● TOF–E–spectrometer for reactions with σ > 1 μb ● Multiple reflection TOF spectrometer plus injection system for separation and isotope ID ► Present RIB intensities do not allow for synthesis of SHN in fusion but allow for the study and application of quasifission, fusion-fission etc.

  24. Collaborating Institutes – GSI Helmholtzzentrum, Darmstadt – Justus-Liebig-Universität Gießen – Joint Institute for Nuclear Reactions, Dubna, Russia – RIKEN Nishina Center for Accelerator-based Science, Japan – Japan Atomic Energy Agency

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