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Production of rare nuclear species with proton and heavy ion beams in various regimes

Production of rare nuclear species with proton and heavy ion beams in various regimes Martin Veselský Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia. Exotic nuclei - only 2500 out of approx 6000 possible nuclei known

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Production of rare nuclear species with proton and heavy ion beams in various regimes

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  1. Production of rare nuclear species with proton and heavy ion beams in various regimes Martin Veselský Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia

  2. Exotic nuclei - only 2500 out of approx 6000 possible nuclei known - large region of very neutron-rich nuclei still unknown - region of superheavy nuclei Physics questions - properties of nuclear surface ( neutron skin ) - nuclear astrophysics ( r-process ) - hyperheavy nuclei, nuclear molecules

  3. Participant-spectator reactions at relativistic energies ( above 100 AMeV ). Applicable to both spallation reactions ( normal kinematics ) and fragmentation ( inverse kinematics ) ?

  4. Production of exotic nuclei in spallation with proton beams ISOLDE facility ( CERN ), beam energies ~ 1 GeVA,

  5. FRS Production of exotic nuclei in relativistic fragmentation Separator FRS ( GSI Darmstadt ), beam energy 1 GeVA, Separátor LISE ( GANIL ), beam energy 70-100 MeVA.

  6. Task 11 - Subtask 1- Heavy Ion Benefits for Driver Accelerator Driver-Beam Scenarios to be Covered 1. The three HI driver beam options described in the report of the Driver Accelerator group (App. B, Sect. 4.2 of the EURISOL report) a) A/q = 2 at 43 A MeV and A/q = 3 at 28 A MeV b) A/q = 2 at 500 A MeV c) A/q = 3 at 100 A MeV and A/q = 2 at 150 A MeV 2. The HI driver beam option described in the Target and Ion Source group (App C, Sect. 2.2.3 of the EURISOL report) A/q = 6 at 166.5 A MeV and A/q = 3 at 333 A MeV 3. 3He beam accelerated to 1 A GeV in the main linac with minor cavity modifications. All these options will be compared with the standard 1 GeV proton-driver case.

  7. Nucleus-nucleus collisions at beam energies below 100 AMeV: - peripheral elastic and quasi-elastic ( QE ) collisions - semi-peripheral deep-inelastic collisions ( DIT ) collisions - incomplete ( ICF ) and complete ( CF ) fusion in central collisions - pre-equilibrium emision typically preceding ICF/CF and DIT ( detailed description in M. Veselský, Nuclear Physics A 705(2002)191 )

  8. Experiments at fragment separator MARS ( Cyclotron Lab, Texas A&M University ).

  9. 86Kr + 64Ni at 25 AMeV Standard DIT ( Tassan-Got and Stefan, NPA 524 (1991) 121 ) Solid - GEMINI, dash-SMM

  10. 86Kr + 64Ni at 25 AMeV Modified DIT (nucl-th/0507026, to appear in NPA): solid - GEMINI, dash -SMM

  11. 86Kr + 124Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM

  12. 86Kr + 124Sn at 25 AMeV Modified DIT (nucl-th/0507026): solid - GEMINI, dash -SMM

  13. 86Kr + 112Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM

  14. 86Kr + 112Sn at 25 AMeV Modified DIT (nucl-th/0507026): Dash-dotted - SMM, s > 0.8 fm solid - GEMINI, dash -SMM

  15. How to reach the extremely neutron-rich nuclei ( e.g. around 78Ni ) : - Optimize projectile-target combination - Optimize energy. Energies lower than 20 AMeV ?

  16. How close to e.g. 78Ni can one get with 86Kr+64Ni at 25 AMeV? Experimental data ( 1-3 deg ) vs modified DIT + SMM

  17. What are the total ( angle-integrated ) cross sections ?

  18. With 86Kr one cannot get too close to 78Ni, how about 82Se ? Calculated yields for reaction 82Se+64Ni at 25 AMeV.

  19. Calculated yields for reaction 82Se+64Ni at 15 AMeV.

  20. Reaction 82Se+64Ni - results of simulations : - cross sections of exotic nuclei around 78Ni at 0.1 - 1 b level - cross sections depend weakly on beam energy - with 100pnA beam, 20 mg/cm2 target ( settings assumed in G. Souliotis et al. PLB 543 (2002) 163 ), the intensities of secondary beams around 78Ni of 10 - 100 /s can be expected - what is the maximum achievable current of the primary beam ?

  21. Observed excess of neutron-rich nuclei in reactions 124Sn+124Sn at 20 AMeV . solid symbols - experimental data open symbols - DIT+Gemini dashed line - EPAX

  22. Test of low energy data 58Ni+208Pb at 5.66 AMeV, angle-integrated data ( L. Corradi et al., Phys. Rev. C 66 (2002) 24606 ) Z=28 Z=26 Z=25 Z=27 Z=24 Z=23 Z=22 Experimental data vs DIT calculation ( after de-excitation )

  23. DIT calculation with radius of nuclear potential extended by 0.75 fm. Possible explanation : deformation, neck structure ? Z=28 Z=26 Z=25 Z=27 Z=24 Z=23 Z=22

  24. DIT calculation ( with extended radius of the nuclear potential ) for the reaction 64Ni+208Pb at 5.66 AMeV, angle-integrated data ( compared to experimental data for the reaction 58Ni+208Pb from L. Corradi et al., Phys. Rev. C 66 (2002) 24606 )

  25. M.B. Tsang et al., PRL 86(2001)5023 G. Souliotis et al., PRC 68(2003)24605 Isoscaling in nuclear processes M. Veselský et al., PRC 69(2004)44607

  26. Comparison of various scenarios - production cross sections compared, others factors such as target thickness, extraction efficiencies are important - region around 78Ni selected as a test case - spallation - GSI model used ( statistical abrasion-ablasion + de-excitation/fission ) - fragmentation - cross sections calculated using EPAX-2, optimized for each isotope over all stable beams

  27. Calculated ( GSI model ) cross sections for 1 GeV proton beam colliding with U, Th, W and La (solid, dashed, dash-dotted and dotted lines, respectively).

  28. Calculated ( GSI model ) cross sections for 1 GeV proton beam colliding with U (solid line), compared to cross sections measured at GSI (P. Armbruster et al., PRL 93 (2004) 212701).

  29. Calculated cross sections for 1 GeV proton beam colliding with U (solid line), compared to the optimal fragmentation cross sections (dashed line ), calculated with EPAX-2 for each nuclide separately using all -stable beams .

  30. Calculated cross sections for 1 GeV proton beam colliding with La (solid line), compared to fragmentation cross sections , calculated with EPAX-2 using La beam and using all -stable beams ( dash-dotted and dashed lines ).

  31. Calculated cross sections for 1 GeV proton beam colliding with U (solid line), compared to the calculated inclusive cross sections for reactions 86Kr,82Se+64Ni at 25 AMeV (dashed and dash-dotted line, respectively) and optimal fragmentation cross sections (dotted line).

  32. Relative cross sections calculated with EPAX-2 for each nuclide separately using all -stable beams in one-step and two-step scenarios (solid and dashed line, respectively).

  33. Contour plot of fragmentation cross sections (dashed lines ), calculated for 78Ni with EPAX-2 using both stable ( dash-dotted line ) and unstable beams .

  34. Conclusions : - spallation/fission, fragmentation and peripheral ( deep-inelastic ) collisions were considered as possible candidates for production of exotic ( neutron-rich ) nuclei around 78Ni - U-target is optimal for spallation/fission with 1 GeV proton beam - cross sections in peripheral ( deep-inelastic ) collisions largest of all for the most n-rich nuclei, technically plausible to explore them ? - systematic cross sections data from peripheral ( deep-inelastic ) collisions are necessary at both Fermi-energy domain and low energies

  35. Extras

  36. 86Kr + 64Ni at 25 AMeV, Exp. vs. Sim. vs Sim. ICF-only

  37. 86Kr + 238U at 28 AMeV, Sim. vs Sim. ICF-only

  38. 82Se + 238U at 28 AMeV, Sim. vs Sim. ICF-only

  39. Experiment (COMBAS) PE+DIT/ICF+SMM 18O + 181Ta at 35 AMeV, carbon isotopes

  40. Experiment (COMBAS) PE+DIT/ICF+SMM 7Be 7Be 18O + 181Ta at 35 AMeV, beryllium isotopes 7Be - fast component, intense pre-eq emission, ICF kinematically impossible, motion along classical Coulomb trajectory ? Transparency ?

  41. EURISOL - 6FP Project "EURISOL Design Study" started in Feb 2005 ( MV/Bratislava involved ) http://www.eurisol-ds.lnl.infn.it/ - theoretical and experimental studies of production mechanisms are planned - open question - Heavy Ion capability for driver accelerator - yes or no ? - selection of the key experiment(s)

  42. Observed excess of neutron-rich nuclei in reactions 86Kr+64Ni at 25 AMeV. solid symbols - experimental data open symbols - DIT+Gemini dashed line - EPAX

  43. Correlation of skin thickness to isovector chemical potential (V. Kolomietz et al, PRC 64(2001)024315, extended Thomas-Fermi calculation) - ἸἩRn-Rp determines the difference of N/Z at (Rn+Rp)/2 ( surface ) from the bulk N/Z, correlates to isovector chemical potential - DIT (T-G) : macroscopic formula for ἸἩRn-Rp used, values unrealistically large but bulk N/Z dynamics described well

  44. Modified DIT (nucl-th/0507026), phenomenological correction, effect of shell structure on nuclear periphery ( assuming validity of the Rn-Rp vs n-p correlation ) and thus on transfer probability estimated as: where S... = S...exp - S...mac ,  is a free parameter (  = 0.53 determined as optimal value ), s > 0 fm ( only non-overlapping configurations considered )

  45. Conclusions 86Kr + 64Ni, 112,124Sn at 25 AMeV - a correction to DIT describes the effect of isospin asymmetry at nuclear periphery - inversion of the bulk isospin flow due to microscopic structure at nuclear periphery - consistent parameters  for all reactions - SMM reproduces the yields of n-rich species well while overestimating the yields of -stable isotopes close to the projectile - GEMINI typically overestimates the width of mass distributions - for p-rich target 112Sn stronger Coulomb interaction supresses the effect of isospin asymmetry at nuclear periphery at s < 1 fm

  46. Conclusions - low energy - deep-inelastic collisions a dominant mechanism for production of exotic nuclei - systematic cross section data needed

  47. Fragment separator VAMOS ( GANIL Caen ) - angular acceptance 9 deg for beam energies 5-100 AMeV.

  48. Production of extremely neutron-rich nuclei - two-step process. Experiment approved at GSI ( a part of EURISOL effort ). Primary target Separation of secondary beam Secondary target Identification of final products

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