1. Spectroscopic studies of moderately neutron-rich nuclei with the CLARA-PRISMA setup
Jose Javier Valiente Dobón (INFN-LNL, Italy)
On behalf of the CLARA-PRISMA collaboration

2. Overview Grazing reactions as a tool to populate neutron-rich nuclei
The CLARA-PRISMA setup
Neutron-rich Copper nuclei
Neutron-rich Fe nuclei
Lifetime measurements of n-rich nuclei: RDDS + CLARA-PRISMA
Future: AGATA for lifetimes measurements at LNL
Summary

3. Grazing reactions LAB. Tool to populate neutron-rich nuclei
Fission 238U
Grazing Target-like
LAB.
Grazing Beam-like
Target
Beam
Substantial kinetic energy damping and mass exchange while retaining partial memory and entrance-channel masses and charges
82Se + 238U, E=505 MeV
G.de Angelis, G.Duchêne

4. Population of states 59Mn 160Dy
Population of yrast or near-yrast states.
Part of the input of the angular momentum of the reaction goes into intrinsic angular momentum. It is less efficient than fusion-evaporation.
The case that converts more transational energy into rotational energy, in a semiclassical picture, is where the projectile and target stick together, and each nucleus rotates around its own centre at the same speed.
59Mn
160Dy
Maximum I ≈ 30ħ
Thick target
Maximum I ≈ 8ħ
Thin target
37Cl+160Gd 234MeV EUROBALL
70Zn+238U 460MeV CLARA+PRISMA
X. Liang et al., Eur. Phys. J. A 10, 41 (2001)
J.J. Valiente-Dobon et al., PRC (2008)

5. The CLARA-PRISMA setup
Laboratori Nazionali di Legnaro (INFN), Italy
PRISMA
Gamma spectrometer
CLARA
Magnetic spectrometer
PRISMA
CLARA

6. The CLARA spectrometer
23 Euroball Clover detectors with anti-Compton
Efficiency ~ 3 % (Eγ= 1.3 MeV)
FWHM = 0.9% (for β=10%)
 spectrum
CLARA spectrometer
A. Gadea et al., Eur. Phys. J. A20 (2004) 193.

7. The PRISMA spectrometer
Large-acceptance magnetic spectrometer
Formed by 1 Q, 1 D and detectors (MCP,MWPPAC, IC) to track the ions.
ΔΩ = 80 msr, ΔZ/Z  1/60, ΔA/A  1/190, Bρ = 1.2 T.m
Identifies nuclei produced in the reaction (A,Z,β) event by event
S. Beghini et al., NIM A551, 364 (2005)
G. Montagnoli et al., NIM A547, 455 (2005)

8. Nuclear structure studies using DIC
CLARA-PRISMA setup Ca Ti Cr Fe Ni Zn Ga Mn Sc V Co Cu 28 32 34 40 50 30
Shell evolution Cu
New region of deformation
Lifetime measurements

9. The Cu isotopes, towards N=50
onto 238U
Investigate the monopole migration and the evolution of the single-particle levels along Z=28 line towards N=50.
1f7/2
2p3/2
1f5/2
2p1/2
1g9/2  
Z=28
N=40
(f7/2)-1
7/2-
7/2-
p3/22+ (A-1Ni)
p1/2
T. Otsuka et al. PRL 95, (2005)
1/2-
f5/2
5/2-
f5/2-p3/2
inversion?
3/2-
p3/2
67Cu38
69Cu40
71Cu42
73Cu44
75Cu46
g9/2
B. Zeidman et al., PRC 18, 2122(1978);R. Grzywacz et al., PRL 81, 766 (1998);S. Franchoo et al., PRL 81, 3100(1998).

10. E. Sahin and G. De Angelis (to be published)
The Cu isotopes, towards N=50
onto 238U
From β-decay, Coulex, deep-inelastic we can disentangle the nature of the excitations in neutron-rich Cu isotopes and therefore the shell evolution along Z=28. More information needed ...
[πf5/2]
[πp3/2]
[π f7/2-1]
[πp3/2θ2+]
[πf5/2θ2+]
( )
( )
( )
E. Sahin and G. De Angelis (to be published)

11. Coming experiments French-Italian collaboration
Weakening of the Z=28 gap by the tensor force in neutron-rich copper isotopes.
Fragmentation of a 76Ge beam at GANIL to reach the π(f7/2)-1states by means of AZn(d,3He) A-1Cu proton pickup in inverse kinematics
Spokepersons: S. Franchoo (Orsay), J.J. Valiente-Dobon (LNL-INFN)
75-77Cu: probing the Z=28 shell gap around doubly magic 78Ni.
Deep inelastic reaction using inverse kinematics VAMOS-EXOGAM
Spokepersons: E. Sahin (LNL-INFN), G. De France (GANIL)

12. Neutron-rich Fe nuclei
onto 238U
Shell model calculations: Core 48Ca
valence space: full fp for protons
p3/2,f5/2, p1/2, g9/2 for neutrons
Fe isotopes evolve towards more collective structures when approaching N=40 → This could be understood in terms of a decrease in the energy gap between the fp shell and the g9/2 when the f7/2 proton shell is not completely filled and more neutrons are excited to the upper shell.
N=40
S. Lunardi et al., PRC 76, (2007)

13. Beyond N=40 in Fe isotopes
Comparison 64Ni and 70Zn onto 238U
64Ni+238U
70Zn+238U 64 60 28 27 26 25 24 36 35 34 62 Ni Co Fe Mn Cr 37 38 66
- 2p
+4n 40 39 70 66 30 29 28 27 26 40 39 38 37 68 Zn Cu Ni Co Fe
- 4p 41 42

14. N=40 and N=42 Fe isotopes N=40 N=42 70Zn@460MeV onto 238U
The experimental level schemes seem to be more quadrupole-collective than the calculated ones. This quadrupole collectivity can be produced by including the d5/2
shell in the model space (A. Zuker et al., PRC52 R1741 (1995)).
S.M. Lenzi et al., LNL Annual Report 2007 and to be published

15. Lifetime measurements
Recoil Distance Doppler Shift method (RDDS) + CLARA-PRISMA Eγ
Eγ’
CLARA
Placed at the θgrazing for BLF
Eγ’ Eγ
Eγ’: Doppler corrected
PRISMA
β’≈8.0%
natMg
Beam 48Ca
Good Mass Resolution
β≈10.0%
Ebeam=310MeV d
Degrader
Target
208Pb
Plunger setup (Koln)
Multi-nucleon transfer reactions

16. Lifetime of the 2+ in 50Ca Is Iu 48Ca τ = 96 ± 3 ps
Gamma spectra, lifetime
τ = 96 ± 3 ps Is Iu
48Ca
J.J. Valiente-Dobón et al., LNL Annual Report 2007 and to be published

17. Effective charges in the fp shell
Full fp shell with a 40Ca core.
GQR (isoscalar)
GQR (isovector)
f7/2
p3/2
p1/2
f5/2 fp
40Ca
CORE
Effective charges take into account the core polarization, that can be understood in terms of the coupling between the particles and the collective oscillations associated with deformations of the core.
Nuclear Structure, Bohr and Mottelson.

18. Effective charges in the fp shell
Full fp shell with a 40Ca core.
ISOSCALAR + ISOVECTOR:
(eeff)pE2=1.15e
(eeff)nE2=0.8e
The obtained effective charges (IS) are different to the ones obtained nearby N≈Z (IS+IV) → Possible isospin dependence of the effective charges.

19. Collectivity of Fe isotopes (N=40)
Two weeks ago it was performed an experiment for lifetime measurments at GANIL, using inverse kinematics of a 238U beam onto a 64Ni target with a natMg degrader (VAMOS+EXOGAM)
Study of 62Fe 64Fe, collectivity towards the N=40
Spokepersons: W. Korten (Saclay), A. Gadea (LNL-INFN, CSIC-Valencia)
Analysis ongoing
Courtesy A. Goergen

20. Simulations for AGATA + PRISMA
CLARA vs. AGATA
AGATA: Talk by E. Farnea
Degrader
Target
Beam
PRISMA
Lifetime measurements
AGATA 0o – 45°
εAD ≈ 6%
Cologne Plunger
γ-γ coincidences
AGATA
CLARA
Lifetime τ=100ps Degrader natMg 4 mg/cm2
Plunger setup (Koln) + AD-PRISMA
Courtesy D. Mengoni

21. Summary
Grazing reactions are a good tool to populate n-rich nuclei at medium spins
Copper siotopes to prove the shell evolution of the Z=28 towards 78Ni. Efforts at LNL and GANIL.
Population of medium mass nuclei A≈60 Fe, showing that these structures evolve towards higher collectivity (LNL) → Lifetimes at GANIL
Novel method to measure lifetimes that combines the traditional RDDS method with the CLARA-PRISMA spectrometers. Lifetimes of the N=30 isotones 50Ca and 51Sc. Determination of the effective charges in the fp shell.
Future at LNL: The AGATA demostrator.
Common interests and collaboration among the french-italian community in the study of neutron-rich nuclei.

22. The CLARA-PRISMA collaboration
France IPHC (IReS) Strasbourg GANIL Caen
U.K. University of Manchester Daresbury Laboratory University of Surrey University of Paisley
Germany HMI Berlin GSI Darmstadt
Poland IFJ-PAN Kraków
Croatia
Ruder Boskovic Institute
Italy INFN LNL-Legnaro University of Padova INFN University of Milano INFN University of Genova INFN University of Torino INFN University of Napoli INFN University of Firenze University of Camerino
Spain University of Salamanca
Romania
Horia Hulubei NIPNE

23. GANIL 75Cu isomers Ganil-Lise Isomeric Chart Data
Tentative spin assignments for the two isomers in 75Cu based on lifetimes and extrapolating the collectivity from 73Cu
Estimates:
T1/2(3/2-)~30 μs
T1/2(M1+E2)(1/2-) ≤ 700 ns
(1/2-)
(3/2-)
(5/2-)

24. Experimental Technique
Thick-target measurements:
No channel selection
Recoiling binary fragments stop inside target
Visible γ rays from states with cumulative half-life 1 ps
High-resolving power multi-detector Ge array
Thin-target measurements:
Channel selection using large solid-angle magnetic spectrometer Legnaro;
In-beam γ-rays measured with multi-detector Ge array in coincidence with detected binary fragments
High efficiency required for γ-γ coincidences

25. The N=50 isotones, towards 78Ni
onto 238U
Three protons away from 78Ni
E. Sahin and G. De Angelis (to be published)

26. The N=50 isotones Z=31 2d5/2 1g7/2 1g9/2 Level schemes N=50
The level schemes have been determined based on:
angular distribution as well as systematics
γ-γ coincidences, thick target experiment (GASP, GAMMASPHERE)
1g9/2
1g7/2
2d5/2
3s1/2
N=50
Shell Model calcuations: 2p-2h excitations across the N=50 shell to 2d5/2-1g7/2-3s1/2 (Lisetsky) for 4.7 MeV of the shell gap value→No reduction of the shell gap

27. Spectroscopy studies around 136Xe
onto 238U
The heaviest system performed with the CLARA-PRISMA setup.
Analysis Ongoing
Courtesy F. Recchia and A. Howard

28. Neutron-rich Mn nuclei
onto 238U fp
fpg fp
fpg
Full fp-shell calculations with KB3G and GXPF1A effective
Interactions.
N=32
N=34
N=36
N=38
Higher spins needed
fp+g9/2 shell space are considered in the calculations done with the fpg effective interaction. The fpg calculations improve for N≥36.
J.J. Valiente-Dobon et al., PRC (2008)

29. Courtesy E. Farnea and A. Gadea
The AGATA demonstrator array
Objective of the AGATA R&D phase
Main issue is Doppler correction capability  coupling to beam and recoil tracking devices
PRISMA
5 asymmetric triple-clusters
36-fold segmented crystals
555 digital-channels
Eff. 3 – 7 Mg = 1
Eff. 2 – 4 Mg = 30 On-line PSA and γ-ray tracking In beam Commissioning
First Test Site:
Laboratori Nazionali di Legnaro
Powerful array in its own right
Still to decide where to site
Still to decide the key test experiments
Courtesy E. Farnea and A. Gadea

30. The AGATA demostrator at LNL
The first subset of AGATA (the Demonstrator Array) will soon start operation at the Laboratori Nazionali di Legnaro. The installation is in progress.
AGATA Triple Cluster
Telescopic beam line