unbound states in dripline nuclei

V. Lapoux DAPNIA/SPhN EURISOL 16-20 Jan. 06

Physics & InstrumentationTrento, 16-20 January 2006

Drip-lines : limit of nuclear binding, large isospinExploration : new structures EXOTIC NUCLEI Tests : nuclear modelling & interactions VNN(Tz)

Probe the structure & spectroscopy at large isospinMeasure unbound states

Tools & detection devices

n , p

Extension of the systematics of neutron excitation along isotopic chains

Unbound states in dripline nuclei


Nuclear structure towards the drip-lines : phenomena to explore & to understand

Neutron skins

halo,clusters

Change in shell structureNew magic numbersLocal properties (N,Z)

4He

6Hehalo

8He4He

Neutron skin

Evolution of structure

at large isospin ?

2006 : what is known ?2016 : area to explore ?


Search for low-lying resonances and study of neutron excitations

MUST : Y.Blumenfeld et al., NIM A421, 421 (‘99)

CATS : S. Ottini et al., NIM A431, 476 (‘99).

beam

MUST (8 in a wall)

+ CATS

(p,p’) probe(p,p’) probeParticle spectroscopy

AAZ (p,p’) Z (p,p’)

p’

AZAZ* A-1Z +n …

p

Beam profile : CATS 1 & 2

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 structurenew magic numbers

Neutron-rich 20,22O


Prototype of (p,p’) & direct reactions at low energy : 8He(p,p’) SPIRAL beam MUST+CATS

structure of 8He : + 4n?

0+

2+

Sn =2.5S4n =3.1

S2n = 2.1

8He

3.6MeV?

>>> Specific tools direct reactions in inverse kinematics

and missing mass method

Unbound excited states, low-lying resonances of weakly-bound nuclei :

A.Lagoyannis et al., 6He(p,p’) @ Ganil, PLB 518, 27 (‘01) .

6He : 2n-halo 8He : neutron-skinResonances of 7,8He

Exotic structures


88HeHe excitation energy spectrum

1n transfer : 8He(p,d)77HeHe

g.s 0+

2+

2n Transfer 8He(p,t)66HeHe

8He +p @ 15.6 MeV/n

F. Skaza, PhD thesis SPhN

Unbound states studies : what we have learnt from SPIRAL beamUnbound states studies : what we have learnt from SPIRAL beam

E405S experiment, MUST collab.

* Large (p,d), (p,t) cross sections• DWBA not valid • GENERAL framework : Coupled Reactions calc. needed, PLB619, 82 (‘05)

Structure of the Structure of the 88He nucleus via direct reactions on proton targetHe nucleus via direct reactions on proton target

2+ 3.62 ± 0.14 MeV Γ = 0.3 ± 0.2 MeV? 5.4 ± 0.5 MeV Γ = 0.3 ± 0.5 MeV


Nuclear landscape towards the drip-lines

2 4 6 8 10 12 14

N

16

2

4

6He

6

Z8

4He

borromeanHe

C

N

O

Hn

pp d t8He

11Li

F 31

Li

Be14Be

B

12

1922

23

24

20020066

Which drip-line nuclei have their identity card complete ?Masses, size, densities, neutron excitation, low-lying spectroscopy,Shell structure ?

6He

Drip-line : 8He neutron-skin


Nuclear landscape towards the drip-lines

16 18 20 22 24 26 28

N

30

18

Z

4He

20020066

10

12

14

16

8

Low-lying resonances ?Neutron skin ?Density Profiles ?New shell effects ?

structure of 24O ? 24O23N22C

31F

30,31,32Ne

33Na

34Mg 38Mg

Next drip-line nuclei ?

37Na36

33

39

Tarasov97Sakurai97Notani02,Lukyanov02

43Si


neutrons

fp

sd

d5/2

d3/2

s1/2

stability

f7/2

p3/2

sd-fpsd-fp 2020

N = 16Z=14 30Si

N = 20

88

N = 8p3/2

p1/2

s1/2

Shell effects far away from stability with new generations of RIB s

Local properties (Z,N)N=34,40,70 instead of N=50,82 ? EURISOL

systematics of neutron excitations vs N Search for new magic numbers

neutrons

fp

sd

d5/2

d3/2

s1/2

drip-line N = 16, Z=8, 24O

f7/2

p3/2

sd-fp

N = 14 22O

N = 16

N = 8

16

N=16 Learnt from 1st generation of RIBs

(1h11/2-)1

2

82(f7/2)


82825050

5050

?

2828

4040

110Zr

132-140...Sn

78Ni2020

2020

88

22

2288

8282

7070

28

neutron drip-line known up to Z=8 (24O)…

doubly magic stable nuclei

doubly magic unstable nuclei ?

drip-lines & properties in the vicinity of new doubly magic nuclei ?

Explorations of nuclear landscape using SPIRAL2, GSI, EURISOL beams Explorations of nuclear landscape using SPIRAL2, GSI, EURISOL beams

FAIR


Z

N

2016 :2016 : 10 years of exploitation of SPIRAL2

Regions of the chart of nuclei accessible with SPIRAL2 beamsPrimary beams: deuterons heavy ions


Z

N

EURISOL

EURISOL

the 109/s beams of EURISOL are the 104 /s of SPIRAL2 and co.

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

Will all our beams be as intense as we believe ???

2016 :2016 : starting EURISOL beams


Alpha-clustersstates

Skin and halos

Soft collective modes

Evolution of neutron excitationMn vs N along isotopic chains

Exotic shapes and resonances

One-particle stateSpectroscopic factors

Beams Variety A,ZLimit of nuclear binding, I

2009+ 2016+

Z

N

Going closer to driplines with higher intensities : opened physics fields

Which beams ? We want to gain in exoticity Which beams ? We want to gain in exoticity

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)

Examples : 38Ne (if not unbound), 60-70Ca, 104Se (Z=34, N=70)

Far ..far away


0+

2+

S2n =7.91

Sn = 4.95

96Kr

6? MeV?

Calc : M.V. Stoitsov, et al., Phys. Rev. C68, 054312 (‘03)Data AME2003

0+

4+

S2n =8.5

Sn = 5.2

94Kr

?

0.67 MeV

1.52

2+

Similar trend for allneutron-rich EURISOL beams :few bound states


100 mm

MUST : ~30cm behind !MUST : ~30cm behind !

~10cm

compactness due to ASIC technology allowsparticle - coincidences

MUST 1 MUST 1 MUST 2: MUST 2: factor 3 larger active areafactor 3 larger active area factor 6 smaller volume of PAfactor 6 smaller volume of PA better time resolutionbetter time resolution

NEW GENERATION of MUST array

NIM A421, 421 (‘99)

MUST2 developed by: DAPNIA/SEDI : µ-electronics R&D ASIC GANIL IPN Orsay

6x6

cm2

Si Strips 300 m

Si(Li) 3mm

CsI1.5 cm

MUST

collaboration : CEA-DAPNIA, GANIL, IPN Orsay

Si(Li)Si(Li)4.5 4.5 mmmm

CsI 3 cmCsI 3 cm4 x 4 4 x 4 segmentssegments

Si stripsSi strips300 300 mm100 x 100 100 x 100 mmmm22

X, Y , T, E128X128Y

E

MUST2MUST22004-62004-6MUr à STrips 2


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) transfersSpin & parity via transfer on polarized targets

Probes, reactions and beam energies

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

collaboration MUST2 : DAPNIA, GANIL, IPN-Orsay

Assets :Assets : beam tracking + LCP arraysE-TOF,E-DE, ID

Experimental method

Direct reactionsAnalysis :MicroscopicMicroscopic potentials potentials Coupled channels+CDCC

0+

2+ ?


20 c.m

40 c.m

Structure studies from direct reactions with EURISOL beams (100MeV/n)

small uncertainty in Theta(LAB) huge variation in excitation energies


60 c.m80 c.m

20 c.m

Structure studies from direct reactions with EURISOL beams (25MeV/n)


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 totE-De and E-TOF correlations for identificationlow E threshold needed ~ < 300 KeVto measure small c.m. angles

* KinematicsReconstruction of the Scattering angle for variable (!) beam optical qualityangle & impact on target required

* Coupling with Gamma-spectroscopy, Compacity

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 stagestop : 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 keVDE resolution (with thin target ~ 1mg/cm2) ~ 400-700 keV Precision on centroid, bound states ~ 30 keV resonant states ~ 100-200 keV ASICs

Requirements for improved charged particle spectroscopyCharged-Particle spectroscopyCharged-Particle spectroscopy needed to explore unbound states(p,p’), (p,d) (p,t) (d,p) Thin light targets p, dE ~ 400keV to 1 MeV


Detection for EURISOL experiments

78Ni +p p’ + 78Ni* p + 76Ni + 2n

p’ + 78Ni* p + 74Ni + 4n

Phase space background due to neutrons produced by decaying unbound states

78Ni +p d + 77Ni unbound? d + 76Ni + n

d + 77Ni* d + 74Ni + 3n

78Ni +p t + 76Ni t + 76Ni* t + 75Ni* + n

t + 74Ni + 2nID, E vs Theta of LCP

78Ni(p,p’)78Ni*

78Ni(p,t)76Ni

78Ni(p,d)77Ni

+ AZ ID of forward focused heavy fragments :Spectrometer orSiLi, CSI arrays close to targets ?

+ neutron detection

Low Sn, S2n, S4n,…

Check alpha-neutronscorrelations ::needsLCP and neutron devices granularity & efficiency


Improved detection for EURISOL experiments

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

Charged-Particle spectroscopyCharged-Particle spectroscopy needed to explore unbound

states Thin light targets p, d

E ~ 400keV to 1 MeV (p,p’), (p,d) (p,t)

+Inverse kinematics :

good Energy resolution in Eexcrequires : beam profile on target

beam tracking detectorsbeam tracking detectors

+ Gamma-ray spectroscopyGamma-ray spectroscopy

needed to separate needed to separate close excited statesclose excited states

Thick target E ~ 20keV (d,p) @ 9 MeV/n

2016 Wishes for Coupled Detection devices


EURISOL : specific experiments and beams

Exotic structure at the neutron drip-line :Ex : 24O 34-38NeComplete the systematic studies of neutron excitation vs N from Z=8 to Z=28 chains EURISOL

Cluster structures : alpha-n correlations & molecular bandsEx : 30Ne : 5 Alpha + 10 n

Probes : (p,p’) + transfer reactions+ (p,2p)


EURISOL : specific experiments and beams

Present (1st generation) intensities : few part/sNeeded : (at least) 103-105 /s

20-50 MeV/n : enough

Looking back in the past !See multi-nucleon transfer

Ex : 9Be(13C,14O)8He H. Bohlen et al., ZPhysA 330 (’88)

10Be(12C,14O)8He Th. Stolla et al., ZPhysA 356 (’96)

SPIRAL2 production of light exotic nucleiR&D for a 9Be target allowing 40 kW beam

SIMILAR TECHNIQUES FOR EURISOL ?


conclusions

Means BEAMS OF RARE BEAMS OF RARE ISOTOPESISOTOPESToday 1/s, EURISOL 103-105 /s

Means DIRECT PROBESi.E p &d targets,+ Polarized p,d DIRECT REACTIONS

target: cryogenic D2 or CD2

Light charged particle (LCP) detection

-ray detection: future AGATA

exotic beamexotic beam EURISOLEURISOLAAZZ

identification

Beam TrackingDevices BTD

A+1A+1ZZp

Einc ~ 20-50 MeV/nNearly (~90%) pure beam


Diffusion (p,p’) en cinDiffusion (p,p’) en cinéématique inversematique inverse

CATS 2

détection du faisceau (x,y,t)

Pre-Amps

Si Strip 6x6 cm2

MUST

Si Strips 300 m

Si(Li) 3mm

CsI1.5 cm

détection d’ions légers x,y,E,t) Z & A (1,2,3H, 3,4He)• gamme étendue E E+E+E• bas seuil (~ 500 keV)• Résolution en positionx, y ~ 1 mm

MUST Y. Blumenfeldet al.,NIM A421 (‘99) 471

CATS S. Ottini et al.,NIM A431 (‘99) 476


+ Information cruciale apportée par les détecteurs de faisceau

11C (p,p ’) @ 40,6 MeV/nucléon : l ’effet des CATS sur MUST

Analyse : Cédric JOUANNE, Thèse 98-01, CEA-Saclay, DSM/DAPNIA/SPhNC. Jouanne, V. L et al., PRC 72, 014308 (’05)

précision centroïde ~ 30keV

E* = 750 keV

réactions de référence


AZ(p,d)A-1Z

Q = Sn(A+1,Z)-Sn(d) = Sn(A+1,Z) - 2.24 MeV

Q(p,d)= Sn(d)-Sn(A,Z) = 2.224 -Sn

AZ(p,t)A-2Z Q(p,t)=S2n(t)-S2n(A,Z) = 8.482 –S2n

Q 8He(p,t) = 6.34

Ex : Q 8He(p,d) = -0.35

0+

2+

Sn =2.5

S4n =3.1

S2n = 2.1

8He

3.6MeV

?AZ(d,p)A+1Z

Q [96Kr(p,d) ]~ - 2.8MeV Q [96Kr(p,t) ]~ - 0.45 MeV

TOOL :TOOL : direct reactions (p,p) (p,d) (p,alpha) & (d,d) (d,p) (d,3He)

Q 8He(p,) = 3.57MeV

Q [ 81Cu(p,) 78Ni] ~ 7MeV81Cu (~80-82Zn) I ~ 105 /s

Using the A+3Z+1 nucleus with higher I to produce and excite AZ

For beams Ispiral2 > ~ 104 /s

Typical conditions for transfer reactions ~ 1mb / srBeams 10 4-5 ppsS ~ 10 - 15 % errord/d ~ 10 - 15 %Beam time ~ 2 weeks

Sn, S2n weak : High cross sections for the 1n, 2n transfer compared to elastic

+ to extend the transfer structure studies more suitable range of beam E for (d,p) : E ~ 10-20 MeV/n

angular momentum window, selectivity134Sn(d,p) 135Sn @ 4.9 MeV/n L ~ 2.5 @ 1010 MeV/n L ~ 3.2

unbound states in dripline nuclei

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