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Unbound states in dripline nuclei

Drip-lines : limit of nuclear binding, large isospin Exploration : new structures EXOTIC NUCLEI Tests : nuclear modelling & interactions V NN (T z ). Extension of the systematics of neutron excitation along isotopic chains.  n ,  p.

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Unbound states in dripline nuclei

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  1. Drip-lines : limit of nuclear binding, large isospin Exploration : new structures EXOTIC NUCLEI Tests : nuclear modelling & interactions VNN(Tz) Extension of the systematics of neutron excitation along isotopic chains n , p • Probe the structure & spectroscopy at large isospin • Measure unbound states Tools & detection devices EURISOL Unbound states in dripline nuclei Physics & Instrumentation Trento, 16-20 January 2006

  2. Nuclear structure towards the drip-lines : phenomena to explore & to understand Neutron skin halo 6He 8He 4He 4He Change in shell structure New magic numbers Local properties (N,Z) Neutron skins halo,clusters Evolution of structure at large isospin ? 2006 : what is known ? 2016 : area to explore ?

  3. Search for low-lying resonances and study of neutron excitations AZ (p,p’) AZ AZ*  A-1Z +n … p p’ Beam profile : CATS 1 & 2 beam MUST (8 in a wall) + CATS Present techniques & results (p,p’) probe Particle spectroscopy Detection of the light charged recoil particle in a dedicated array  the strip-wall device MUST bound excited states close to thr : E. Khan et al., 20O(p,p’) PLB 490 (‘00) 45 C. Jouanne, V. L., et al., 10,11C(p,p’) PRC 72, 014308 (’05) Modification of the usual shell structure new magic numbers Neutron-rich 20,22O MUST : Y.Blumenfeld et al., NIM A421, 421 (‘99) CATS : S. Ottini et al., NIM A431, 476 (‘99).

  4. Unbound states of exotic nuclei via direct reactions Unbound excited states, low-lying resonances of weakly-bound nuclei : A.Lagoyannis et al., 6He(p,p’) @ Ganil, PLB 518, 27 (‘01) . ? 3.6MeV 2+ S4n=3.1 Exotic structures 6He : 2n-halo 8He : neutron-skin Resonances of 7,8He Sn=2.5 structure of 8He :  + 4n? S2n= 2.1 0+ 8He Prototype of (p,p’) & direct reactions at low energy : 8He(p,p’) SPIRAL beam MUST+CATS >>> Specific tools direct reactions in inverse kinematics and missing mass method exotic He isotopes

  5. Unbound states studies : what we have learnt from SPIRAL beam g.s 0+ 2+ Structure of the 8He nucleus via direct reactions on proton target 2n Transfer 8He(p,t)6He E405S experiment, MUST collab. 8Heexcitation energy spectrum 8He +p @ 15.6 MeV/n 2+ 3.62 ± 0.14 MeV Γ = 0.3 ± 0.2 MeV ? 5.4 ± 0.5 MeV Γ= 0.3 ± 0.5 MeV 1n transfer : 8He(p,d)7He • * Large (p,d), (p,t) • cross sections • DWBA not valid • GENERAL framework : • Coupled Reactions calc. • needed, PLB619, 82 (‘05) F. Skaza, PhD thesis SPhN

  6. Nuclear landscape towards the drip-lines 2006 Nuclear landscape towards the drip-lines 31 F 24 O 8 23 N Z C 12 22 6 19 B 4 Be 14Be 4He Li 11Li 2 He p p d t 6He H 8He borromean n N 2 4 6 8 10 12 14 16 6He Testing ground Which drip-line nuclei have their identity card complete ? Masses, size, densities, neutron excitation, low-lying spectroscopy, Shell structure ? Drip-line : 8He neutron-skin

  7. Nuclear landscape towards the drip-lines 2006 Nuclear landscape towards the drip-lines Next drip-line nuclei ? N 36 33 39 16 18 20 22 24 26 28 30 Testing ground 18 Z 16 43Si 14 34Mg 38Mg 12 33Na 37Na Low-lying resonances ? Neutron skin ? Density Profiles ? New shell effects ? 4He 10 30,31,32Ne Tarasov97 Sakurai97 Notani02, Lukyanov02 31F 8 24O structure of 24O ? 23N 22C

  8. Shell effects far away from stability with new generations of RIB s 20 8 neutrons stability neutrons drip-line N = 16, Z=8, 24O p3/2 fp 16 f7/2 p3/2 fp sd-fp f7/2 sd-fp d3/2 d3/2 N = 20 sd s1/2 sd N = 16 Z=14 30Si d5/2 s1/2 N = 16 d5/2 p1/2 N = 14 22O N = 8 p3/2 N=16  Learnt from 1st generation of RIBs N = 8 s1/2 82 (f7/2) Local properties (Z,N) N=34,40,70 instead of N=50,82 ?  EURISOL (1h11/2-)12 systematics of neutron excitations vs N Search for new magic numbers

  9. Explorations of nuclear landscape using SPIRAL2, GSI, EURISOL beams drip-lines & properties in the vicinity of new doubly magic nuclei ? doubly magic stable nuclei doubly magic unstable nuclei? 82 50 50 40 132-140...Sn 20 82 28 70 ? 20 110Zr FAIR 78Ni 8 2 8 neutron drip-line known up to Z=8 (24O)… 28 2

  10. 2016 : 10 years of exploitation of SPIRAL2 Z N Regions of the chart of nuclei accessible with SPIRAL2 beams Primary beams:  deuterons  heavy ions

  11. 2016 : starting EURISOL beams EURISOL Will all our beams be as intense as we believe ??? the 109/s beams of EURISOL are the 104 /s of SPIRAL2 and co. Z EURISOL If the beams are new (36Ne ? 60-68Ca ?) or rare at present (24O few/s at GANIL, RIKEN) with EURISOL : counting rates less or around 103-105 /s N

  12. Exotic shapes and resonances Z Which beams ? We want to gain in exoticity One-particle state Spectroscopic factors Prospectives Complete the (p,p’) chains O (24O), Ne + Mg, Si, S, Ar +spectroscopy of neutron-rich around N=28, N=40 (new), N=50, N=70 (new) Evolution of neutron excitation Mn vs Nalong isotopic chains 2009+ 2016+ Examples : 38Ne (if not unbound), 60-70Ca, 104Se (Z=34, N=70) Beams Variety A,Z Limit of nuclear binding, I  SPIRAL2 EURISOL N Skin and halos Going closer to driplines with higher intensities : opened physics fields Soft collective modes Alpha-clusters states Far ..far away

  13. Unbound states of exotic nuclei S2n=8.5 ? Sn= 5.2 1.52 4+ 2+ 0.67 MeV 0+ 94Kr S2n=7.91 2+ ? 6? MeV Sn= 4.95 0+ 96Kr Similar trend for all neutron-rich EURISOL beams : few bound states Calc : M.V. Stoitsov, et al., Phys. Rev. C68, 054312 (‘03) Data AME2003

  14. Improved techniques MUr àSTrips2 2004-6 CsI 1.5 cm MUST2 Si (Li) 3mm Si Strips 300 m compactness due to ASIC technology allows particle -  coincidences collaboration : CEA-DAPNIA, GANIL, IPN Orsay • MUST 1  MUST 2: • factor 3 larger active area • factor 6 smaller volume of PA • better time resolution MUST : ~30cm behind ! Si(Li) 4.5 mm Si strips 300 m 100 x 100 mm2 X, Y , T, E 128X 128Y DE CsI 3 cm 4 x 4 segments MUST ~10cm 100 mm 6x6 cm2 NEW GENERATION of MUST array NIM A421, 421 (‘99) • MUST2 developed by: • DAPNIA/SEDI : µ-electronics R&D ASIC • GANIL • IPN Orsay

  15. Experimental method Direct reactions Analysis : Microscopic potentials Coupled channels +CDCC Assets :beam tracking + LCP arrays E-TOF,E-DE, ID collaboration MUST2 : DAPNIA, GANIL, IPN-Orsay ? 2+ 0+ Probes, reactions and beam energies Measure a complete set of direct reactions : investigation of nuclear structure form factors (densities) + Neutron excitations via (p,p ’) spectroscopic factors via (d,p) (p,d) transfers Spin & parity via transfer on polarized targets At which energies do we need to accelerate ? Optimize between : Energies required by physics case & experimental difficulties 1. Access to high energy excited states : higher Einc compared to SPIRAL2 2. energy resolution for excitation energies  lower Einc

  16. Structure studies from direct reactions with EURISOL beams (100MeV/n) 40c.m 20c.m small uncertainty in Theta(LAB)  huge variation in excitation energies

  17. Structure studies from direct reactions with EURISOL beams (25MeV/n) 80c.m 60c.m 20c.m

  18. Requirements for improved charged particle spectroscopy • Charged-Particle spectroscopy needed to exploreunbound states • (p,p’), (p,d) (p,t)(d,p) Thin light targets p, d DE ~ 400keV to 1 MeV Means…  array of Si strip telescopes  stage-telescopes Si + SiLi +CSI  For each channel,TAC for TOF, DT (part. det) ~ 500 ps to ~ 1ns start : particle in the Si stage stop : time before target : beam detector  2 beam tracking detectors for x,y, T event by event 1mm x-y, 300 ps DT ~ 0.5deg MUST@ 15 cm Intrinsic DE (Si) ~ 50 keV DE resolution (with thin target ~ 1mg/cm2) ~ 400-700 keV Precision on centroid, bound states ~ 30 keV resonant states ~ 100-200 keV  ASICs particle spectroscopy, requirements * Angular coverage (FWD and BWD)  4 & Granularity (Dx ~ Dy ~ 1mm) * Large Dynamics and Particle Id [p,d,t, 3,4,6,8He 6Li Energies up to ~ 300 MeV tot E-De and E-TOF correlations for identification low E threshold needed ~ < 300 KeV to measure small c.m. angles * Kinematics Reconstruction of the Scattering angle for variable (!) beam optical quality angle & impact on target required * Coupling with Gamma-spectroscopy,  Compacity

  19. Detection for EURISOL experiments Low Sn, S2n, S4n,… Phase space background due to neutrons produced by decaying unbound states + AZ IDof forward focused heavy fragments : Spectrometer or SiLi, CSI arrays close to targets ? + neutron detection 78Ni(p,p’)78Ni* 78Ni +p  p’ + 78Ni*  p + 76Ni + 2n p’ +78Ni*  p + 74Ni + 4n 78Ni(p,d)77Ni 78Ni +p  d + 77Ni unbound? d + 76Ni + n d +77Ni*  d + 74Ni + 3n Check alpha-neutrons correlations :: needs LCP and neutron devices granularity & efficiency 78Ni(p,t)76Ni 78Ni +p   t + 76Ni  t + 76Ni*  t + 75Ni* + n  t + 74Ni + 2n ID, E vs Theta of LCP

  20. 2016 Wishes for Coupled Detection devices Improved detection for EURISOL experiments • Charged-Particle spectroscopy • needed to exploreunbound states • Thin light targets p, d • DE ~ 400keV to 1 MeV • (p,p’), (p,d) (p,t) • + • Inverse kinematics : • good Energy resolution in Eexc • requires : beam profile on target • beam tracking detectors + • Gamma-ray spectroscopy • needed to separate close excited states • Thick target DE ~ 20keV • (d,p) @ 9 MeV/n Steps beyond in the detection : - ASIC technology (Application Specific Integrated Circuit) (compacity of all devices) - Mixed detection (gamma+ charged particles +… neutrons) : Ex : Ge + Si + scintillator in a crystal-Ge-Si ball array -Higher multiplicities in LCP arrays (3,4,..) challenges in acquisition systems : synchronize separated arrays & triggers needs to reduce dead time + A,Z ID of heavy fragment in a spectrometer or SiLi CsI array +NEUTRON DETECTION

  21. EURISOL : specific experiments and beams Exotic structure at the neutron drip-line : Ex : 24O 34-38Ne Complete the systematic studies of neutron excitation vs N from Z=8 to Z=28 chains  EURISOL Cluster structures : alpha-n correlations & molecular bands Ex : 30Ne : 5 Alpha + 10 n Probes : (p,p’) + transfer reactions + (p,2p)

  22. EURISOL : specific experiments and beams SPIRAL2 production of light exotic nuclei R&D for a 9Be target allowing 40 kW beam SIMILAR TECHNIQUES FOR EURISOL ? Intensities Present (1st generation) intensities : few part/s Needed : (at least) 103-105 /s Energies 20-50 MeV/n : enough Production modes Looking back in the past ! See multi-nucleon transfer Ex : 9Be(13C,14O)8HeH. Bohlen et al., ZPhysA 330 (’88) 10Be(12C,14O)8HeTh. Stolla et al., ZPhysA 356 (’96)

  23. conclusions conclusions ... prospectives EURISOL p target: cryogenic D2 or CD2 exotic beam EURISOL AZ identification A+1Z Beam Tracking Devices BTD structure of drip-line nuclei -ray detection: future AGATA Light charged particle (LCP) detection Means BEAMS OF RARE ISOTOPES Today 1/s, EURISOL 103-105 /s Means DIRECT PROBES i.E p &d targets, + Polarized p,d DIRECT REACTIONS Einc ~ 20-50 MeV/n Nearly (~90%) pure beam

  24. Diffusion (p,p’) en cinématique inverse CsI 1.5 cm Si (Li) 3mm Si Strips 300 m Pre-Amps Si Strip 6x6 cm2 MUST • détection d’ions légers • x,y,E,t) Z & A (1,2,3H, 3,4He) • gamme étendue EDE+DE+E • bas seuil (~ 500 keV) • Résolution en position • Dx, Dy ~ 1 mm détection du faisceau (x,y,t) CATS 2 CATS S. Ottini et al., NIM A431 (‘99) 476 MUST Y. Blumenfeld et al., NIM A421 (‘99) 471

  25. 11C (p,p ’) @ 40,6 MeV/nucléon : l ’effet des CATS sur MUST + Information cruciale apportée par les détecteurs de faisceau DE* = 750 keV précision centroïde ~ 30keV réactions de référence Analyse : Cédric JOUANNE, Thèse 98-01, CEA-Saclay, DSM/DAPNIA/SPhN C. Jouanne, V. L et al., PRC 72, 014308 (’05)

  26. Unbound states of exotic nuclei via direct reactions + to extend the transfer structure studies • more suitable range of beam E for (d,p) : E ~ 10-20 MeV/n ? 3.6MeV 2+ S4n=3.1 Sn=2.5 S2n= 2.1 Sn, S2n weak : High cross sections for the 1n, 2n transfer compared to elastic 0+ 8He Typicalconditions for transfer reactions  ~ 1mb / sr Beams  10 4-5 pps S ~ 10 - 15 % error d/d ~ 10 - 15 % Beam time ~ 2 weeks angular momentum window, selectivity 134Sn(d,p) 135Sn @ 4.9 MeV/nL ~ 2.5@ 10MeV/n L ~ 3.2 For beams Ispiral2 > ~ 104 /s TOOL :direct reactions (p,p) (p,d) (p,alpha) & (d,d) (d,p) (d,3He) AZ(d,p)A+1Z Q = Sn(A+1,Z)-Sn(d) =Sn(A+1,Z) - 2.24 MeV AZ(p,d)A-1Z Q(p,d)= Sn(d)-Sn(A,Z) = 2.224 -Sn Q(p,t)=S2n(t)-S2n(A,Z) = 8.482 –S2n Ex : Q 8He(p,d) = -0.35 AZ(p,t)A-2Z Q 8He(p,t) = 6.34 Q [96Kr(p,d) ]~ - 2.8MeV Q [96Kr(p,t) ]~ - 0.45 MeV Q 8He(p,a) = 3.57MeV Using the A+3Z+1 nucleus with higher I to produce and excite AZ 81Cu (~80-82Zn) I ~ 105 /s Q [ 81Cu(p,a) 78Ni] ~ 7MeV

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