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Studies of single-particle structure of exotic nuclei using Transfer R eactio ns

Studies of single-particle structure of exotic nuclei using Transfer R eactio ns. B. Fern á ndez-Dom í nguez & TIARA collaboration. University of Liverpool. MOTIVATION. Magic Numbers below 40 Ca. 40 Ca. stable. N=Z. proton rich. 20. neutron rich. 32 Mg. 26 Ne. X. 16 O. 28 O. 24 O.

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Studies of single-particle structure of exotic nuclei using Transfer R eactio ns

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  1. Studies of single-particle structure of exotic nuclei using Transfer Reactions B. Fernández-Domínguez & TIARA collaboration University of Liverpool

  2. MOTIVATION Magic Numbers below 40Ca 40Ca stable N=Z proton rich 20 neutron rich 32Mg 26Ne X 16O 28O 24O 20 8 16 T. Otsuka et al. Phys. Rev. Lett.87 (2001) 082502. -V monopole interaction between p(d5/2)xn(d3/2) rises the n(d3/2) level up close to the pf shell • Evolution of single particle structure • Disappearance of shell gaps • Position of neutron drip line

  3. d,t 25Na 24Ne 23Ne 26Ne 25Ne 27Ne 23F 24F 25F Applying transfer reactions to exotic nuclei : Experimental constraints d,3He d,p • Low intensities (104 pps) mean • high efficiency required • Finite target thickness (1 mg/cm2) • limits the resolution (200 keV) • We want to develop a general • technique for all mass beams • … with good resolution Goal of the experiment: Study of the influence of the N=16 shell closure across the Ne isotopes using single nucleon transfer reactions

  4. 24Ne (SPIRAL) beam @ 10.5 A MeV (GANIL) + EXOGAM Gamma-ray array VAMOS spectrometer radioactive beams - 24Ne (SPIRAL) 10.5 A MeV TIARA silicon array active beam Stop ( finger ) Triple coincidences: Target-like particles - TIARA Beam-like particles - VAMOS Gammas - EXOGAM Trigger: hit in TIARA CD2 target 1mg/cm2 Detectors DE, E, TOF Br, q, f

  5. Beam-like particles identification : VAMOS VAMOS TIARA+EXOGAM beam Scintillator Plastic Drift Chambers Ionisation Chamber Identification method: Full Z, A/q identification • DE-E->Z • X,Y(event-by-event reconstruction)->Br • TOF->v • Br-v->A/q

  6. Ejectiles, angular distribution : VAMOS+TIARA DE(a.u.) VAMOS A/q (a.u) TIARA (d,t) (d,d) (d,p) TIARA TIARA TIARA

  7. M. Labiche GEANT4 Ejectiles, angular distribution : TIARA (d,p) (d,t) (d,d) TIARA TIARA TIARA

  8. g-g coincidences in EXOGAM +TIARA ALL 1.7 MeV 1.7+2.0 MeV 2.0 MeV 3.3 MeV 4.0 MeV

  9. 24Ne(d,p)25Ne Proton Angular Distributions • W. Catford et al., J. Phys. G 31 (2005) S1655. ground state Ex = g.s.  = 0 DWBA calculations (Surrey, TWOFNR code) excited states Ex = 1.70 MeV  = 2 Ex = 2.05 MeV = 2

  10. W. Catford et al., Eur. Phys. J. A 25 (2005) 245. C2S 24Ne (d,p) 25Ne ( = 3) 4060 4030 5/2+ 0.73 7/2 – 4.0 p = – 7/2+ 3330 9/2+ 3290 0.75 3/2 –  = 1 0.004 5/2+ 3.0 0.11 3/2+  =2 2030 0.44 2030 3/2+ Excitation Energy (MeV) 2.0 5/2+ 0.10 1703 1680 0.15 5/2+  =2 3/2+ 0.49 1.0 n+24Negs  = 0 1/2+ 0.0 0.80 1/2+ 0.63 Other Reactions (Literature) Fitting error Present Work USD +/- sigma

  11. Systematics of the 3/2+ in the N=15 isotones 27Mg 23O 25Ne 4.5 4.0 1f7/2 3.5 3.0 excitation energy (MeV) 2.5 2.0 1d5/2 1.5 1d3/2 1.0 1s, 1p 1s, 1p 1s, 1p 1s, 1p 1s, 1p 1s, 1p 0.5 2s1/2 0.0 8 10 12 6 atomic number • 23O from USD shell model and M.Stanoiu et al., PRC 69 (2004) 034312. • 25Ne preliminary result. The energy of the 1d3/2 neutron orbital rises when protons are removed from its spin-orbit partner, the 1d5/2 orbital. 25Ne10 27Mg12 23O8 1d3/2 1d3/2 1d3/2 2s1/2 2s1/2 2s1/2 1d5/2 1d5/2 1d5/2 n n n p p p

  12. Summary • TIARA+VAMOS+EXOGAM is an excellent tool to study transfer reactions with radioactive beams • First experiments have provided new information on 25Ne and the evolution of N=16 gap

  13. TIARA collaboration W.N. Catford 1, C.N. Timis 1, M. Labiche 3, R. C. Lemmon2, R. Chapman 3, B. Rubio 4, L. Caballero 4, N. Amzal 1, N. I. Ashwood 5, T.D. Baldwin 1, M. Burns 3, M. Chartier 6, N. Curtis 5, G. de France 7, W. Gelletly1, X. Liang 3,M. Freer 5, N.A. Orr 8, S. Pain 1, V.P.E Pucknell 3, M. Rejmund 7, H. Savajols 7, O. Sorlin 9, K. Spohr 3, C. Theisen 10, D.D. Warner 2. (1) Department of Physics, University of Surrey, Guildford GU2 5XH, UK. (2) Daresbury Laboratory, Warrington, WA4 4AD, UK. (3) The Institute of Physical Research, University of Paisley, Paisley PA1 2BE, UK. (4) Instituto de Fisica Corpuscular, Valencia, Spain. (5) School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK. (6) Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK. (7) Grand Accélérateur National d’Ions Lourds, 14000 Caen, France. (8) Laboratoire de Physique Corpusculaire, 14000 Caen, France. (9) Institut de Physique Nucléaire d’Orsay, 91406 Orsay, France. (10) Commissariat d’Energie Atomique de Saclay, 91191 Gif-sur-Yvette, France

  14. SLIDES AFTER THIS POINT ARE NOT PART OF THE TALK

  15. Analysis (d,p) reaction Fitting with angle-dependent widths FWHM 1100 keV Barrel (resistive) FWHM 500 keV Hyball (strip) C. Timis

  16. 24Ne(d,p)25Ne Proton Angular Distributions negative parity states Ex = 3.33 MeV  = 1 Ex = 4.03 MeV ( = 3) DWBA calculations (TWOFNR code)

  17. Simultaneously measuring the elastic scattering gives an internal absolute calibration for the cross section

  18. g-g coincidences in EXOGAM g gated on 4.05 MeV protons and Vamos g gated on 4.05 MeV protons, Vamos and 1.7 MeV g All g gated on protons g gated on 4.05 MeV protons, vamos and 2.35MeV g Entry at 4.05 MeV all p-gamma events Energy in TIARA Experimental g-spectra

  19. Target Changing Mechanism Barrel Si 36 < lab < 144  300 mm Beam VAMOS Target position Forward Annular Si (S1+S2) 5.6 < lab < 28  Backward Annular Si 144 < lab < 168.5  Target-like particles : TIARA DX=0.4 mm, Dq=2o (Barrel) DX=0.4 mm, Dq=0.7o (Hyball)

  20. Front Side Gamma-ray: EXOGAM Exogam Segmented Clover • 4 large co-axial n-type Germanium detectors • Diameter >60 mm, length >90 mm before shaping • Strong tapering, 30 mm angle 22.50 • Outer contact segmented longitudinally splitting the crystal into 4 quadrants • 4 high resolution inner contacts, 16 position outputs from outer contacts. Energy Resolution: 50 KeV (FWHM) at 1.9 MeV Photopeak efficiency: 17% at 1.322 MeV

  21. TIARA Si Array Developments • Particle Identification • - second Si layer of barrel • Si-CsI array at forward angles • MUST-2 ?

  22. re-acceleration production secondary reaction target • Beam from SPIRAL • RIB 24Ne at 10 A.MeV • 1  105 pps at 8 mm.msr • Pure • Well-focussed - no tracking • CD2 target 1.0 mg/cm2 • Inverse kinematics • Triple coincidence • VAMOS in dispersive mode

  23. Detailed Géant4 Simulations 4030 Entry at 4.0 MeV 3330  = 2 2030 1680  = 0

  24. : Experimental Set-up Momentum accepance Δp/p = ± 5% Angular acceptance Δx, Δy = 160 mrad Solid angle ΔΩ = 100 msr Dispersion D = 2 cm/% Flight path length L = 7.3 m

  25. : foc Zgoubi  Fin Xfoc in Ffoc  Yfoc Trajectories Reconstruction • Calculation of high-order transfer elements COSY INFINITY , solution of the equation motion, and inversion of the transfer matrix . (MSU) • Database of 10000 trajectories, ZGOUBI including TOSCA field charts,to map the whole space θin and Φin. Χ2 - minimisation to determine the coefficients. (GANIL) H. Savajols Nucl. Instr. And Meth. In Phys. Res. B 204 (2003)

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