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Elastic scattering of halo projectiles at low energies

Elastic scattering of halo projectiles at low energies. Outline Introduction – RIB in the world The RIBRAS (Radioactive Ion Beams in Brasil) system Elastic scattering of 6 He on 120 Sn, 58 Ni, 27 Al and 9 Be targets Experiments with the double solenoid system

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Elastic scattering of halo projectiles at low energies

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  1. Elastic scattering of halo projectiles at low energies Outline • Introduction – RIB in the world • The RIBRAS (Radioactive Ion Beams in Brasil) system • Elastic scattering of 6He on 120Sn, 58Ni, 27Al and 9Be targets • Experiments with the double solenoid system • A diffractive model for elastic scattering of exotic nuclei R. Lichtenthäler

  2. Introduction – RIB in the world Nuclides chart in 1965 and in 2011 ~1200 known presently ~ 3500 and 283 stable protons neutrons protons neutrons R. Lichtenthäler

  3. Introduction – RIB in the world The ends of the nuclear landscape • Halos and skins • Borromean nuclei (3-body systems) • New magic numbers and quenching of the shell gaps. • Importance in astrophysics – overcoming the A=5,8 gap synthesis of elements heavier than Fe • New shapes and deformations – fundamental symmetries • Superheavy elements R. Lichtenthäler

  4. Introduction – RIB in the world Light exotic nuclei unstable proton rich 17Ne 10 20Ne 22Ne unstable neutron rich 9 2p-halo 19F 8 16O 17O 18O 18 20 22 stable 7 14N 8B 6 12C 13C neutron halo 16 8B 10B 1p-halo 5 11B 24O proton halo 7Be 9Be 10Be 4 12 14 proton number 10 weakly bound 3 6Li 7Li 8Li 9Li 2 4He 8He 8 3He borromean 1 4 6 1H 2H 3H 11Be n 2 double magic 1 11Li 6He 1n-halo neutron number nucleus S.E(MeV) (structure) 11Li (T1/2=8.75ms) 0.300 (n+n+9Li) 6He (T1/2=807ms)0.973 (2n+alfa) 11Be (T1/2=13.81s) 0.501 (n+10Be) 8B (T1/2=770 ms) 0.137 (p+7Be) 2n-halo R. Lichtenthäler

  5. Introduction – RIB in the world 11Li Lithium isotopes Radius of nucleus (fm) 7Li 8Li 6Li 9Li Number of neutrons Tanihata - 1985 stable R=r0*A1/3 6He But for Halo nuclei: 11Li,6He, 11Be ... R > r0 A1/3 11Li r R 3-body forces Efimov states R. Lichtenthäler

  6. Introduction – RIB in the world Production of Radioactive Ion Beams(RIB) In-flight ISOL • Relatively easy to implement • Intense secondary beams • Not so good beam characteristics: emitance and contaminations More complex implementation Requires a post accelerator Good quality secondary beams R. Lichtenthäler

  7. RIB in the world Dubna Lanzhou Present intensities ~ 105 to 107 pps future: RIKEN (japão), SPIRAL2 (França), FAIR (GSI), FRIB(EUA)‏ intensities will be of ~ 109 – 1012 pps !! R. Lichtenthäler

  8. The RIBRAS system The São Paulo Pelletron Laboratory primary Li,Be,B,C,O,Si,Cl I~500nAe-mAe RIBRAS – since 2004 8 UD 2-5 MeV/A R. Lichtenthäler

  9. The RIBRAS system scattering chamber mid scattering chamber primary beam primary target R. Lichtenthäler

  10. The RIBRAS system First solenoid DW=30 msr angular acceptance 2 deg<Dq <6 deg primary beam 1- primary target 2- collimator 3- Faraday cup 4- solenoid 5- lollipop 6-collimator 7- scattering chamber,secondary target and detectors R. Lichtenthäler

  11. The RIBRAS system Intensity (pps) Iprimary ~ 300 nAe SecondaryBeam Production Reaction 6He 9Be(7Li,6He) 10+5 8Li 9Be(7Li,8Li) 10+5 7Be 3He(6Li,7Be) 10+5 7Be 3He(7Li,7Be) 10+5 8B 3He(6Li,8B) 10+4 10Be9Be(11B,10Be) 10+4 7Be 7Li(6Li,7Be) 105 Neutron halo Borromean proton halo Energy of the secondary beams 10-30 MeV depending on the beam. R. Lichtenthäler

  12. The RIBRAS system – identification spectra 8Li (0.98;1+) particle E E 8Li gs 20mm 1000 mm 7Li FWHM=470 keV 9Be(7Li,8Li)8Be cocktail beam 150 mm² Detector at zero deg. no secondary target DE 8Ligs lollipop DE-E telescope 7Li2+ 8Li* 8Li3+ 6He2+ 4He2+ alphas p,d,t R. Lichtenthäler

  13. The RIBRAS system – identification spectra 6He+120Sn 6He+58Ni t 6He+9Be p,d,t 6He+197Au R. Lichtenthäler

  14. Elastic scattering of 6He on several targets Calculations • Optical Model • 3 and 4 body CDCC 4He+51V 6He+51V 6He+9Be 6He+27Al 6He+120Sn R. Lichtenthäler

  15. around the Coulomb barrier: E~Eb q1/4 lg Fraunhofer diffraction type Far side Near side Fresnel diffraction type (Coulomb-nuclear interference) Coulomb+nuclear V Coulomb barrier E above the Coulomb barrier: E>>Eb r 6He+9Be Dq=p/lg ; lg=kR nuclear R. Lichtenthäler

  16. Elastic scattering of 6He on several targets q1/4 lg 4 body CDCC calculations 9,10,11Be+64Zn diPietro et al. 6He+120Sn predictions! Y.Y. Yang et al. 8B+208Pb 6He+208Pb @ 27 MeV R. Lichtenthäler

  17. Elastic scattering of 6He on several targets T n x R 6He n y a T 2n R 6He y a j=7 j=6 j=5 j=4 j=3 contiuum j=2 gs i=1 4-body effects,V. Morcelle et al., PLB 732, 228 (2014) [Ti+Uii-Ei]Yi=UijYj 6He+58Ni Bin U6He-T = <f6He|Ua-T+Un-T+Un-T|f6He> no free parameters 4-body- M. Rodríguez-Gallardo 3 body (Eb=0.973 MeV) and modified 3-body (Eb=1.6 MeV) -K.C.C. Pires and A.M Moro R. Lichtenthäler

  18. Elastic scattering of 6He on several targets T 2n R 6He y a r R K.C.C. Pires et al. PRC (2014) 6He+9Be U6He-T = <f6He|Ua-9Be+U2n-9Be|f6He> where Ua-9Be is known empirically and U2n-9Be is adjusted to fit the data R. Lichtenthäler

  19. Elastic scattering of 6He on several targets 6He+120Sn exotic tightly bound weakly bound shalo=s6He+120Sn-s4He+120Sn Reduced reaction cross section Reaction cross-section obtained from the elastic scattering (CDCC,OM,CC) R. Lichtenthäler

  20. Elastic scattering of 6He on several targets Reduced cross-sections for intermediate mass systems A~60 6He+58Ni 6He+51V 6He+64Zn 8B+58Ni 6Li+51V 9Be+64Zn 6Li+58Ni 6Li+64Zn 7Be+58Ni 4He+58Ni 4He+51V 16O+64Zn exotic weakly bound tightly bound R. Lichtenthäler

  21. Elastic scattering of 6He on several targets Reduced cross section for light systems (9Be target). enhancement R. Lichtenthäler

  22. Elastic scattering of 6He on several targets Percent enhancement for several systems [this work] [this work] [this work] guideline R. Lichtenthäler

  23. Experiments with the double solenoid system scattering chamber mid scattering chamber primary beam primary target R. Lichtenthäler

  24. Experiments with the double solenoid system Crossover mode parallel mode Solenoid 1 Solenoid 2 Primary beam g detector lollipop lollipop lollipop lollipop Secondary target colimator Faraday cup Primary target Solenoid 1 Solenoid 2 Rad. shield 1 meter R. Lichtenthäler

  25. Experiments with the double solenoid system absorber Primary beam Colimator Faraday cup Beam blocker (lollipop) Primary target 6He Beam purity 1 solenoid double solenoid 6He beam 92% purity 6He beam 16% Solenoid 1 Solenoid 2 lollipop R. Lichtenthäler

  26. Experiments with the double solenoid system absorber Primary beam Colimator Faraday cup Beam blocker (lollipop) Primary target 1 solenoid double solenoid 8Li Beam purity Solenoid 1 Solenoid 2 lollipop R. Lichtenthäler

  27. Experiments with the double solenoid system Silicon telescope DE E 50mm 1000mm 11.7 11.2 Ecm+Q 7He 10.8 p+6He ; 9.975 MeV GS ; 0 MeV ; 3/2- 7Li Excitation function measurements. Experiments with the thick target method -resonances in 6He+p=7Li and 8Li+p=9Be. CH2 12 mg/cm2 protons 6He spectrum of light particles E6He=12.2 MeV range resonances in the CN R. Lichtenthäler

  28. p(6He,p)6He p(6He,p)6He excitation functions R. Lichtenthäler

  29. The p(8Li,p)8Li scattering R. Lichtenthäler

  30. Three excitation functions with R-matrix calculations (AZURE) R. Lichtenthäler

  31. A diffractive model for elastic scattering |Sl| 1 D bimpact parameter 0.5 Lg l=kb Ericson parameterization of the S-matrix (1960’s) 3 parameters only; Lg=kLR ; R=r0(Ap1/3+At1/3) ; D=kLa ; a =0.65 fm for stable nuclei  diffuseness a phase (-p/2<a<p/2) R. Lichtenthäler

  32. A diffractive model for elastic scattering Results for 6He and 11Li+208Pb and 6He+9Be R. Lichtenthäler

  33. A diffractive model for elastic scattering L grazing – 6He+208Pb Delta - 6He+208Pb D=ka with a=0.65 fm for the 6He and 11Li+208Pb systems D>>ka due to long range effects: Coulomb x nuclear breakup R. Lichtenthäler

  34. A diffractive model for elastic scattering cos(f) betweennuclear and Coulomb amplitudes cos(f) delta=0.658 delta=4.128 Fresnel peak due to Coulomb – nuclear interference effects A. Diaz-Torrez, PLB (2014) R. Lichtenthäler

  35. Summary • A systematic enhancement was observed in the total reaction cross section of systems with 6He projectiles, with respect to other stable weakly bound projetiles on the several targets. • This enhancement dependends on the mass of the target, being larger for heavier targets. • Experiments using the thick target method are in progress. R. Lichtenthäler

  36. RIBRAS collaboration: Universidade de São Paulo, IFUSP A. Lépine-Szily,R. Lichtenthäler Fo,V. Guimarães, M.A.G. Alvarez, L. Gasques,P. N. deFaria,D.Mendes, K.C.C. Pires, V.Morcelle, E. A. Benjamim, A. Barioni, M.C. Morais, M. Assunção, R. PampaCondori, E.Leistenschneider, O. Camargo Jr., J. Alcantara-Nunez, V. Scarduelli, D. Pereira, M.S. Hussein Universidad de Sevilla, Espanha A.M. Moro, M. Rodríguez-Gallardo Université Libre de Bruxelles P. Descouvemont Laboratorio Tandar, Buenos Aires, Argentina A. Arazi CEADEN, Havana, Cuba I.Padron Universidade Federal Fluminense (UFF) P.R.S. Gomes, J. Lubian, J.M.B. Shorto, D.S. Monteiro University of Notre Dame, EUA J. Kolata Faculty of Science, The M.S. University of Baroda, India Surjit Mukherjee R. Lichtenthäler

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