Transcript New challenges in Nuclear Structure

AGATA
Advanced Gamma-Ray Tracking Array
Next-generation spectrometer based on g-ray tracking
Radioactive and stable beams, high recoil velocities
Bulk crystals operated in position sensitive mode
Very high efficiency and spectrum quality
Collaboration of 12 European countries
R&D programme started in ~1998
Compact 4 germanium array
Total Cost 60 M€
INFN contribution 20÷25 %
Construction period 2004-2008-2018
Experimental Physics program starts in 2008
New challenges in
Nuclear
Structure
Shell structure in nuclei
• Structure of doubly magic nuclei
Shape coexistence
• Changes in the (effective) interactions
Proton drip line and N=Z nuclei
• Spectroscopy beyond the drip line
• Proton-neutron pairing
• Isospin symmetry
48Ni
100Sn
132+xSn
78Ni
Transfermium nuclei
Nuclear shapes
• Exotic shapes and isomers
• Coexistence and transitions
Neutron rich heavy nuclei (N/Z → 2)
• Large neutron skins (rn-r→ 1fm)
• New coherent excitation modes
• Shell quenching
Nuclei at the neutron drip line (Z→25)
• Very large proton-neutron asymmetries
• Resonant excitation modes
• Neutron Decay
Experimental
conditions and challenges
FAIR
SPIRAL2
SPES
EURISOL
REX-ISOLDE
MAFF
High Int. Stable
•
•
•
•
•
Low intensity
High backgrounds
Large Doppler broadening
High counting rates
High g-ray multiplicities
Need instrumentation
High efficiency
High sensitivity
High throughput
Ancillary detectors
AGATA
(Advanced Gamma Tracking Array)
Main features
Efficiency: 40% (Mg=1)
today’s arrays ~10% (gain ~4)
25% (Mg=30)
5% (gain ~1000)
Peak/Total: 65% (Mg=1)
50% (Mg=30)
today
40%
~55%
Angular Resolution: ~1º 
FWHM (1 MeV, v/c=50%) ~ 6 keV !!!
today
~40 keV
Rates: 3 MHz (Mg=1) 300 kHz (Mg=30)
today
1 MHz
20 kHz
180 large-volume, 36-fold segmented, encapsulated HPGe crystals
3 shapes, 60 all equal triple-clusters  solid angle coverage 80 %
6660 high-resolution digital electronics channels
Sophisticated Pulse Shape Analysis  Position sensitive operation mode
 Gamma-ray tracking
The AGATA Collaboration
Bulgaria:
Denmark:
Finland:
France:
Germany:
Hungary:
Italy:
Poland:
Romania:
Sweden:
Turkey:
UK:
Sofia
Copenhagen
Jyväskylä
GANIL, Lyon, Orsay, Saclay, Strasbourg
Berlin, Bonn, GSI, Darmstadt, Köln, München
Debrecen
Padova, Milano, LNL, Firenze, Camerino, Napoli, Genova
Krakow, Swierk, Warsaw
Bucharest
Lund, Stockholm, Uppsala
Ankara, Istanbul
Daresbury, Brighton, Keele, Liverpool, Manchester,
Paisley, Surrey, York
Bold, main financial contribution to the AGATA Demonstrator
AGATA will look like this
4 ball built out of 12 modules of 5 triple-clusters
Fist module of 5 triple clusters  DEMONSTRATOR
Commissioning 2007, Experiments start in 2008
Agata detectors
Crystals
Capsules
Cryostats
Single: for tests and scanning
high-purity Ge
~ 1.5 kg
36-pixels cathode
0.8 mm Al walls
0.4 mm spacing
permanent vacuum
Triple: for AGATA clusters
The Phases of AGATA
5 Clusters
Demonstrator
2007
Peak efficiency
3 – 8 % @ Mg = 1
2 – 4 % @ Mg = 30
Replace/Complement
Main issue is Doppler
correction capability
 coupling to beam and
recoil tracking devices
LNL
PRISMA CLARA
GANIL VAMOS
EXOGAM
GSI
FRS
RISING
JYFL
RITU
Improve resolutionJUROBALL
at higher recoil velocity
Extend spectroscopy to more exotic nuclei
The Phases of AGATA
2010
Efficiency (%)
15 Clusters
1
50
45
Solid Angle (%)
Efficiency M = 1
40
Efficiency M = 10
Efficiency M = 20
35
Efficiency M = 30
30
25
20
15
10
5
0
b = 10
b =2 0.5
The first “real” tracking array
Used at SPIRAL2, FAIR-HISPEC, High Intensity Stable
Coupled to spectrometer, beam tracker, LCP arrays …
Spectroscopy at the N=Z (100Sn), n-drip line nuclei, …
30 Clusters
2
Magnetic
Spectrometer
The Phases of AGATA
Also used as partial arrays in different labs
Coupled to spectrometer, beam tracker, LCP arrays
Spectroscopy at the N=Z (100Sn), n-drip line nuclei, …
45 Clusters
3
Ancillary
The Phases of AGATA
Efficient as a 120-ball (~20 % at high g-multiplicity)
Ideal instrument for FAIR / EURISOL
Also used as partial arrays in different labs
Higher performance by coupling with ancillaries
The Phases of AGATA
60 Clusters
4
Full ball, ideal to study extreme deformations
and the most exotic nuclear species
Most of the time used as partial arrays
Maximum performance by coupling to ancillaries
Status and Evolution
• Demonstrator (5 clusters) ready in 2007
• Next phase (1) discussed in 2005-2006
• New MoU and bids for funds in 2007
• Construction start in 2008
– 1 ready in 2010
(12 M€)
– 2 ready in 2012
– 3 ready in 2015
– 4 ready in 2018
(15 M€)
(15 M€)
(15 M€)
• Total cost  60 M€
(includes 20 % contingency)
(excludes tax and man-power)
Estimated dates. Actual
dates depend on funding
profile and production
capability of detectors
Physics with AGATA
Coulomb excitation
at barrier energies
(~ 102 pps, b < 0.1)
Evolution of shell structure
Collective excitations
Nuclear astrophysics
at intermediate energies
(~ 100 pps, b  0.1 - 0.3)
GDR
Spin-flip transitions
First excited levels
Transfer reactions,
Nucleon knock-out & Coulomb break-up
(> 103-4 pps, b  0.1 - 0.3)
Single particle energies
Angular momentum contributions
Spectroscopic factors
Fragmentation and fusion studies
(106 – 1012 pps, b  0.05- 0.3)
First excited states in nuclei close to the drip lines
Neutron rich nuclei at (very) high spins
Structure of the heaviest nuclei close to the “line of stability”
Long Range Plan 2004
Recommendations
and
priorities
…
In order to exploit present and future facilities
fully
and
most
efficiently,
advanced
instrumentation and detection equipment will be
required to carry on the various programmes.
The project AGATA, for a 4-array of highly
segmented Ge detectors for g-ray detection and
tracking, will benefit research programmes in
the various facilities in Europe. NuPECC gives
full support for the construction of AGATA
and recommends that the R&D phase be
pursued with vigour.
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