Jose Javier Valiente Dobón (INFN-LNL, Italy) On behalf of the CLARA-PRISMA collaboration...
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Transcript of Jose Javier Valiente Dobón (INFN-LNL, Italy) On behalf of the CLARA-PRISMA collaboration...
Jose Javier Valiente Dobón (INFN-LNL, Italy)
On behalf of the CLARA-PRISMA collaboration
Spectroscopic studies of moderately neutron-rich nuclei with the
CLARA-PRISMA setup
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
Grazing reactionsTool to populate neutron-rich nuclei
Target
Beam
Grazing Target-like
Grazing Beam-like
LAB.
Substantial kinetic energy damping and mass exchange while retaining partial memory and
entrance-channel masses and charges
82Se + 238U, E=505 MeV
Fission 238U
G.de Angelis, G.Duchêne
Population of states
•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.
X. Liang et al., Eur. Phys. J. A 10, 41 (2001)
Maximum I ≈ 30ħ
37Cl+160Gd 234MeV EUROBALL
Maximum I ≈ 8ħ
160Dy59Mn
70Zn+238U 460MeV CLARA+PRISMAJ.J. Valiente-Dobon et al., PRC 78 024302 (2008)
Thick target
Thin target
PRISMA
The CLARA-PRISMA setup
• Gamma spectrometer
CLARA
• Magnetic spectrometer
PRISMA
CLARA
Laboratori Nazionali di Legnaro (INFN), Italy
The CLARA spectrometer
• 23 Euroball Clover detectors with anti-Compton
• Efficiency ~ 3 % (Eγ= 1.3 MeV)
• FWHM = 0.9% (for β=10%)
spectrumCLARA spectrometer
A. Gadea et al., Eur. Phys. J. A20 (2004) 193.
The PRISMA 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
I C
MWPPAC
I C
MWPPAC
Large-acceptance magnetic spectrometer
S. Beghini et al., NIM A551, 364 (2005)
G. Montagnoli et al., NIM A547, 455 (2005)
Ca
Ti
Cr
Fe
Ni
ZnGa
Mn
Sc
V
Co
Cu
28 32 34 40 5030
Nuclear structure studies using DIC
Shell evolution Cu Shell evolution Cu
New region of deformation New region of deformation Lifetime measurements Lifetime measurements
CLARA-PRISMA setup
82Se@505MeV onto 238U
The Cu isotopes, towards N=50
Investigate the monopole migration and the
evolution of the single-particle levels along
Z=28 line towards N=50.
g9/2
71Cu42 73Cu4475Cu46
f5/2-p3/2 inversion?
1f7/2
2p3/2
1f5/2
2p1/2
1g9/2
Z=28
N=40
p3/2
f5/2
p1/2
3/2-
5/2-
1/2-
7/2-
67Cu38
7/2-(f7/2)-1
69Cu40
B. Zeidman et al., PRC 18, 2122(1978);R. Grzywacz et al., PRL 81, 766 (1998);S. Franchoo et al., PRL 81, 3100(1998).
p3/22+ (A-1Ni)
T. Otsuka et al. PRL 95, 232502 (2005)
[πf5/2]
[πp3/2]
[π f7/2-1]
[πp3/2θ2+]
[πf5/2θ2+] ( )
( )
( )
( )
( ) ( )
( )
( )( )( )
( )
82Se@505MeV onto 238U
The Cu isotopes, towards N=50
E. S
ahin
and
G. D
e A
ngel
is (
to b
e pu
blis
hed)
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 ...
Coming experiments
•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)
French-Italian collaboration
Neutron-rich Fe nuclei64Ni@400MeV onto 238U
S. Lunardi et al., PRC 76, 034303 (2007)
Shell model calculations: Core 48Cavalence space: full fp for protons p3/2,f5/2, p1/2, g9/2 for neutrons
N=40
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.
64
60
2827
26
25
24
363534
62
Ni
Co
Fe
Mn
Cr
37 38
66- 2p +4n
4039
70
66
3029282726
40393837
68
ZnCuNi
CoFe
- 4p
41 42
Beyond N=40 in Fe isotopes Comparison 64Ni and 70Zn onto 238U
64Ni+238U 70Zn+238U
N=40 N=42
S.M. Lenzi et al., LNL Annual Report 2007 and to be published
70Zn@460MeV onto 238U
N=40 and N=42 Fe isotopes
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)).
229
225 // gf 4
29225 // gf
Lifetime measurements
Beam 48Ca
208Pb
natMg
PRISMA
β≈10.0%
β’≈8.0%
Ebeam=310MeVdDegrader Target
Eγ’ Eγ
CLARA
Recoil Distance Doppler Shift method (RDDS) + CLARA-PRISMA
Eγ Eγ’
Eγ’: Doppler corrected
Good Mass Resolution
Multi-nucleon transfer reactions
Placed at the θgrazing for BLF
Plunger setup (Koln)
Lifetime of the 2+ in 50Ca
Iu
Is
Gamma spectra, lifetime
τ = 96 ± 3 ps
J.J. Valiente-Dobón et al., LNL Annual Report 2007 and to be published
48Ca
Effective charges in the fp shell
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.
GQR (isoscalar)
GQR (isovector)
f7/2
p3/2
p1/2
f5/2fp
40CaCORE
Full fp shell with a 40Ca core.
Nuclear Structure, Bohr and Mottelson.
Effective charges in the fp shellFull fp shell with a 40Ca core.
The obtained effective charges (IS) are different to the ones obtained nearby
N≈Z (IS+IV) → Possible isospin dependence of the effective charges.
ISOSCALAR + ISOVECTOR:
(eeff)pE2=1.15e
(eeff)nE2=0.8e
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)
Analys
is on
going
Courtesy A. Goergen
Simulations for AGATA + PRISMACLARA vs. AGATA
CLARA
AGATA
Lifetime τ=100ps Degrader natMg 4 mg/cm2
Degrader
Target
Bea
mPRISMA
Lifetime measurements
•AGATA 0o – 45°
•εAD ≈ 6%
•Cologne Plunger
•γ-γ coincidences
AGATA: Talk by E. Farnea
Plunger setup (Koln) + AD-PRISMA
Courtesy D. Mengoni
• 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.
Summary
•FranceIPHC (IReS) Strasbourg GANIL Caen
•U.K.University of Manchester Daresbury Laboratory University of Surrey University of Paisley
•GermanyHMI BerlinGSI Darmstadt
•PolandIFJ-PAN Kraków
•CroatiaRuder Boskovic Institute
•ItalyINFN 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
•SpainUniversity of Salamanca
•Romania Horia Hulubei NIPNE
The CLARA-PRISMA collaboration
GANIL 75Cu isomers
(1/2-)
(5/2-)
(3/2-)
http://www.ganil.fr/lise/chart/chart/chart32/75cu.gif
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 μsT1/2(M1+E2)(1/2-) ≤ 700 nns
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 (PRISMA@INFN Legnaro; VAMOS@GANIL)• In-beam γ-rays measured with multi-detector Ge array in coincidence with detected binary fragments• High efficiency required for γ-γ coincidences
82Se@505MeV onto 238U
The N=50 isotones, towards 78Ni
Three protons away from 78Ni
E. Sahin and G. De Angelis (to be published)
Level schemes
The N=50 isotones
The level schemes have been determined based on: •angular distribution as well as systematics•γ-γ coincidences, thick target experiment (GASP, GAMMASPHERE)
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 1g
9/2
1g7/2
2d5/2
3s1/2
N=50
Z=31
Spectroscopy studies around 136Xe136Xe@930MeV onto 238U
The heaviest system performed with the CLARA-PRISMA setup.
Anal
ysis
Ong
oing
Courtesy F. Recchia and A. Howard
Neutron-rich Mn nuclei70Zn@460MeV onto 238U
fpfp fpgfpg
N=38
N=32 N=34
N=36
Full fp-shell calculations with KB3G and GXPF1A effective Interactions.
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 78 024302 (2008)
Higher spins needed
5 asymmetric triple-clusters36-fold segmented crystals555 digital-channels
Eff. 3 – 7 % @ Mg = 1
Eff. 2 – 4 % @ Mg = 30
On-line PSA and γ-ray trackingIn beam CommissioningFirst Test Site:Laboratori Nazionali di Legnaro
Main issue is Doppler correction capability coupling to beam and recoil
tracking devices
PRISMA
The AGATA demonstrator arrayObjective of the AGATA R&D phase 2003-2008
Courtesy E. Farnea and A. Gadea
The first subset of AGATA (the Demonstrator Array) will soon start operation
at the Laboratori Nazionali di Legnaro. The installation is in progress.
The AGATA demostrator at LNL
Telescopic beam line
AGATA Triple Cluster