Transcript Advanced gamma – ray spectroscopy with AGATA

Advanced Gamma–Ray
Spectroscopy Techniques with
the AGATA Segmented
Detectors
Călin A. Ur*
for the AGATA Collaboration
INFN – Sezione di Padova
*On
leave from IFIN–HH Bucharest
Layout
• Principles of the AGATA gamma–ray tracking
array
• Building phases of the array
• The AGATA Demonstrator
• First tests at the National Laboratories of
Legnaro
• Compton imaging with segmented detectors
01/02/2010
ELI NP Workshop Bucharest
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Extreme Experimental Conditions
FAIR
SPIRAL2
SPES
REX-ISOLDE
EURISOL
HI-SIB
•
•
•
•
•
Low intensity
High backgrounds
Large Doppler broadening
High counting rates
High g-ray multiplicities
Need instrumentation
01/02/2010
High efficiency
High sensitivity
High throughput
Ancillary detectors
ELI NP Workshop Bucharest
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Extreme Experimental Conditions
FAIR
SPIRAL2
SPES
REX-ISOLDE
EURISOL
HI-SIB
•
•
•
•
•
Low intensity
High backgrounds
Large Doppler broadening
High counting rates
High g-ray multiplicities
ELI ?
Need instrumentation
01/02/2010
High efficiency
High sensitivity
High throughput
Ancillary detectors
ELI NP Workshop Bucharest
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The New Concept of Tracking Arrays
Gamma Arrays based on Compton
Suppressed Spectrometers
Compton
rejected
AC
Full energy
accepted
AC
EUROBALL
GAMMASPHERE
Tracking Arrays based on
Position Sensitive Ge Detectors
AGATA
e ~ 10 — 7 %
e ~ 50 — 25 %
( Mg=1 — Mg=30)
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GRETA
( Mg=1 — Mg=30)
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Analogue vs Digital Electronics
Present Arrays
E
ADC
t
TDC
CFD
DAQ
Detector
(Germanium)
Shaping
Amplifier
AGATA
NSR
Filters
Segment
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ELI NP Workshop Bucharest
t
t
x,y,z
Detector
E
DAQ
FADC
E
Tracking
Detector
(Germanium)
E
PSA
MWD
t
Array
6
Ingredients of Gamma–Ray Tracking
1
Highly segmented
HPGe detectors
Identified
interaction points
(x,y,z,E,t)i
4
Reconstruction of tracks
evaluating permutations
of interaction points
·
Pulse Shape Analysis
to decompose
recorded waves
·
3
2
Digital electronics
to record and
process segment
signals
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Reconstructed
gamma-rays
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Position Determination – PSA

 

ie/h   qe/h  EW  vdrift E
Calculation of the signals induced on the
contacts using the weighting field method
FEM-model
of detector
 
 
 









net charge signals
Calculate
weighting
fields
*
transient signals








Th. Kröll, NIM A 463 (2001) 227
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Pulse Shape Analysis Concept
A3
A4
A5
(10,10,46)
B3
C3
B4
C4
B5
C5
(10,30,46)
y
CORE
C4
B4
measured
D4
791 keV deposited in segment B4
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x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
B3
B4
B5
C3
C4
C5
(10,10,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
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ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
B3
B4
B5
C3
C4
C5
(10,15,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
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ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
B3
B4
B5
C3
C4
C5
(10,20,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
01/02/2010
ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
B3
B4
B5
C3
C4
C5
(10,25,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
01/02/2010
ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
B3
B4
B5
C3
C4
C5
(10,30,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
01/02/2010
ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Pulse Shape Analysis Concept
A3
A4
A5
Result of
Grid Search
algorithm
B3
C3
B4
C4
B5
C5
R. Venturelli
(10,25,46)
y
CORE
C4
measured
calculated
791 keV deposited in segment B4
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ELI NP Workshop Bucharest
B4
D4
x
A4
E4
F4
z = 46 mm
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Interaction/Reconstruction Algorithms
~ 100 keV
Photoelectric
~1 MeV
Compton Scattering
Isolated hits
Probability of
interaction depth
Angle/Energy
E γ' 
Eγ
1
Eγ
m0c
2
1  cosθ 
~ 10 MeV
g-ray energy
Pair Production
Pattern of hits
E1st = Eg – 2 mc2
Algorithms: ClusterTracking, FuzzyTracking, BackTracking, …
Reconstruction efficiency limited by Position resolution and Compton profile.
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Pulse Shape Analysis Concept
Idealized configuration to determine
maximum attainable performance.
Ri = 15 cm
Ro = 24 cm
230 kg of Ge
A high multiplicity event
Eg = 1.33 MeV
Mg = 30
Events simulated using GEANT4
Response of shell at 1.33 MeV:
eph = 70%
P/T = 77%
Reconstruction by Cluster-Tracking
Packing Distance: 5 mm
Position Resolution: 5 mm (at 100 keV)
1.33 MeV
Mg = 1
Mg = 30
eph (%)
65
36
P/T(%)
85
60
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27 gammas detected -- 23 in photopeak
16 reconstructed
-- 14 in photopeak
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D. Bazzacco
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Possible Array Configurations
A180 is AGATA’s choice
Configuration
120 crystals
180 crystals
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A120
A120F
A120C4
A180
Crystals (shapes)
120 (2)
120 (6)
120 (2)
180 (3)
Clusters (shapes)
40 (2)
40 (2)
30 (1)
60 (2)
Ge solid angle (%)
71.0
77.8
78.0
81.6
Ge weight (kg)
232
225
230
363
Centre to Ge (cm)
19.7
18
18.5
23.5
Electronics channels
4440
4440
4440
6660
Eff. at Mg = 1 (%)
32.9
36.9
36.4
43.3
Eff. at Mg = 30 (%)
20.5
22.0
22.1
28.1
P/T at Mg = 1 (%)
52.9
53.0
51.8
58.2
P/T at Mg = 30 (%)
44.9
43.7
43.4
49.1
GRETA is for A120C4
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The Advanced GAmma Tracking Array
Requirements
efficiency, energy resolution, dynamic range, angular resolution,
timing, counting rate, modularity, angular coverage, inner space
Quantity
Specified for
Target Value
Eγ = 1 MeV, Mγ = 1,  < 0.5
50 %
Eγ = 1 MeV, Mγ = 30,  < 0.5
25 %
Eγ = 10 MeV, Mγ = 1
10 %
Peak-to-total ratio (P/T)
Eγ = 1 MeV, Mγ = 1
60 - 70 %
Eγ = 1 MeV, Mγ = 30
40 - 50 %
Angular resolution (g)
E/E < 1%
Maximum event rates
Mγ = 1
Mγ = 30
Photo-peak efficiency (eph)
Inner space for ancillaries
01/02/2010
better than 1
3 MHz
300 kHz
> 170 mm
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Construction of the AGATA Array
Ge crystals:
Hexaconical shape
90-100 mm long
80 mm max diameter
36 segments
Al encapsulation:
0.4 mm spacing
0.8 mm thickness
Triple clusters:
3 encapsulated crystals
Al end-cap:
2.0 mm spacing
1.0 mm thickness
111 cold FET preamplifiers
Distance between faces of crystals:
in same cluster
~2.5 mm
in adjacent clusters ~9.0 mm
01/02/2010
Total weight of the 60 clusters of the AGATA180 configuration ~2.5 tons
Mounted on a self-supporting structure
ELI NP Workshop Bucharest
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Asymmetric AGATA Triple Cryostat
- integration of 111 high resolution
spectroscopy channels
- cold FET technology for all signals
Challenges:
- mechanical precision
- heat development, LN2 consumption
- microphonics
- noise, high frequencies
FWHM [keV]
@1.3 MeV
@ 60 keV
Core
2.10 keV
@ 1.3 MeV
1.20 keV
@ 60 keV
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ELI NP Workshop Bucharest
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Electronics and DAQ
Fully synchronous system with global
100 MHz clock and time-stamp
distribution (GTS)
Digitizers: 100 Ms/s, 14 bit
Optical fiber read-out of full data
stream to pre-processing electronics
GTS
detector
detector
clk
Preamps
Preamps
Digitizers
Digitizers
Local processing triggered by Ge common
contact. Determine energy and isolate
~ 600 ns of signal around rise-time
Buffers of time-stamped local events sent
to PSA to extract position of interactions
7.4 GB/s/det
Local
processing
Local
processing
100 MB/s/det
@ 50 kHz
PSA
PSA
5 MB/s/det
Trigger-less system. Global trigger possible.
Global event builder and software trigger
Event
Builder
On-line gamma-ray tracking
Tracking
Control and storage (~1 TB/year), …
On line…
Storage …
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…
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The Phases of AGATA 1
5 Clusters
Demonstrator
Our days
Peak efficiency
3 – 8 % @ Mg = 1
2 – 4 % @ Mg = 30
Main issue is Doppler correction capability
coupling to beam and recoil tracking devices
Improve resolution at higher recoil velocity
Extend spectroscopy to more exotic nuclei
01/02/2010
ELI NP Workshop Bucharest
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The Phases of AGATA 2
Near future
Efficiency (%)
15 Clusters
1p
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
The first “real” tracking array
 = 01
 = 0.5
2
Recoil velocity
To be used at FAIR-HISPEC, SPIRAL2, SPES, …
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The Phases of AGATA 3
45 Clusters
3p
Far future
Efficient as a 120 ball (20% at high g multiplicity)
Ideal for FAIR and EURISOL
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The Phases of AGATA 4
60 Clusters
4p
Remote future
Full ball / full performance
Ideal to study extreme deformations and the most
exotic nuclear species
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The AGATA Demonstrator
Objective of the R&D phase 2003-2008
5 asymmetric triple-clusters
36-fold segmented crystals
540 segments
555 digital-channels
Eff. 3 – 7 % @ Mg = 1
Eff. 2 – 4 % @ Mg = 30
Full ACQ
online PSA and g–ray tracking
Cost ~5 M€
Present status
3 asymmetric triple-clusters
mounted&tested at INFN LN Legnaro
+1 in delivery
Undergoing commissioning runs
detectors, DAQ, PSA, online
Physics campaign
to start in ~1 month
01/02/2010
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First in–beam Test at LNL
Week 12 (March 16-22)
• 30Si(@70MeV)+12C fus.–evap. reaction in inverse kinematics
• The system included
– full AGATA DAQ chain
– PSA and tracking performed in real time (online)
• Goal
– test the whole system under real data taking conditions
– test Doppler correction capability of the AGATA detectors
•
01/02/2010
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Doppler Broadening and Position Res.
1  βcos(θ)
E CM

E
γ
γ 1  βcos(θ)
E CM

E
1 β2
γ
γ
1  β2
2
 β, θ and E in Lab frame
 β, θ and E in Lab frame
γ
γ
2
2
 E CM
2
 E CM

 E CM
2
2
2
2
γCM 2
γ
γ
CM 2
CM
CM





ΔE γ 2   E γ  Δθ 2   E γ  Δβ 2   E γ  ΔE γ 2
 θ  Δθ   β  Δβ   E  ΔE 
ΔECM



γ
γ

 β 
 E γ 

θ
γ




 2 
2
2

2




2
 E βsinθ 2 Δθ 2   E β  cosθ   Δβ 2   1  βcosθ 2 ΔE 2
ΔE CM

γ 2
2
1  βcosθ
3 
2
2
 γ β  cosθ
2 
2 
 Eγ βsinθ
2 2  Δβ   
ΔEγCM





Δθ

E
ΔE
1

β
1

β
γ Position
γ 1 β 3 
γ
 γ resolution



2 
2 





1 β 

 1 β 
1  β2 2 









Angular resolution
g ray
Recoil
Beam
Energy resolution
01/02/2010
ELI NP Workshop Bucharest
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Doppler Broadening and Position Res.
40K
1823 keV
 ~ 5%
12.5 keV
full detector
segments (17.7 keV)
PSA+tracking
Full optimization and analysis – 1 month
our target
online
01/02/2010
ELI NP Workshop Bucharest
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Compton Imaging
Compton scattering – a tool for testing the position resolution
• In-beam experiment
– given the position of
the target we track the
g rays
E1

E2
target
g ray
Compton scattering
• Compton imaging
of a radioactive source
– inverse tracking – from
the first 2 interaction
points get the position
of the source
01/02/2010
E1

g-source
E2
g ray
ELI NP Workshop Bucharest
F. Recchia
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Principles of Compton Imaging
 [deg]
 1
1 

cos  1 

m0c 2
E

 g Eg 
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angular error [deg]
Compton Imaging Performance
Sources of error in the identification
of the source direction:
• Position resolution (axis)
• Energy resolution (scattering
angle)
• Compton profile (scattering angle)
01/02/2010
ELI NP Workshop Bucharest
scattering angle [deg]
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Experimental Setup at LNL
Digital DAQ system
provided by IFIN – HH
Bucharest
• 10 x TNT2 NIM
Digitizer boards from
CAEN with 4ch
14bit /100MHz
60Co
01/02/2010
source
ELI NP Workshop Bucharest
AGATA prototype detector
(one symmetric capsule)
34
Comparison with MC Simulations
 profile
of experimental image
Projections
Experiment
peak FWHM [deg]
 [deg]
After PSA
5.2
position resolution FWHM [mm]
f profile
of experimental image
Monte Carlo +
5 mm position resolution
peak FWHM [deg]
 [deg]
f [deg]
MC
MC
4.7
position resolution FWHM [mm]
01/02/2010
ELI NP Workshop Bucharest
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Gamma Background Rejection
characterize the capability of the AGATA detectors to discriminate different
gamma source locations using Compton imaging algorithm
Experimental Setup:
3 g–ray sources 60Co, 152Eu and 137Cs
their positions simulate the beam-dump, the beam line and the target
M. Doncel & F. Recchia
01/02/2010
ELI NP Workshop Bucharest
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Results
a)
E1 = 1173 keV
E2 = 1332 keV
Spectra of the gamma radiation
assigned to each source position
with the algorithm
Spectra assignment
a) corresponds to the 60Co position
b) corresponds to the 137Cs position
c) corresponds to the 152Eu position
•promising results
•need more refinement of the method
01/02/2010
b)
E = 661 keV
c)
ELI NP Workshop Bucharest
E = 344 keV
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Outlook
To exploit the present and future facilities fully and most
efficiently, advanced instrumentation and detection
equipment is required – NuPECC recommendation
The 4p-array of highly segmented Ge detectors AGATA
for g-ray detection and tracking is part of this effort
First measurements in-beam and with sources show
that the position resolution is ~ 5 mm FWHM; this value
is in line with the design assumptions of the AGATA
spectrometer, confirming the feasibility of g-ray tracking
AGATA will have a strong impact on nuclear structure
studies : lifetime measurements of nuclear states down
to
fs,
angular
distribution
and
polarization
measurements
Is AGATA or part of it of interest for the ELI project?
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ELI NP Workshop Bucharest
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The AGATA Collaboration
Bulgaria:
Denmark:
Finland:
France:
Germany:
Hungary:
Italy:
Poland:
Romania:
Sweden:
Turkey:
UK:
01/02/2010
Sofia
Copenhagen
Jyväskylä
GANIL, Lyon, Orsay, Saclay, Strasbourg
Berlin, Bonn, GSI, Darmstadt, Jülich, 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
ELI NP Workshop Bucharest
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Outlook
01/02/2010
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First in–beam test with STC
Position resolution extracted through a
comparison to detailed Monte Carlo
simulations (FWHM vs. pos. resolution)
~5.2
Symmetric triple cluster
mm
4.8 keV
11 keV
experiment performed at
IKP of Cologne
32 keV
01/02/2010
Silicon detector
ELI NP Workshop Bucharest
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New Challenges from the RIB Facilities
Shell structure in nuclei
• Structure of doubly magic nuclei
• Changes in the (effective) interactions
Proton drip line and N=Z nuclei
• Spectroscopy beyond the drip line
• Proton-neutron pairing
• Isospin symmetry
Nuclear shapes
• Exotic shapes and isomers
• Coexistence and transitions
Neutron rich heavy nuclei (N/Z → 2)
• Large neutron skins (rn-rp→ 1fm)
• Shell quenching
Nuclear Astrophysics
• Properties of r and rp process nuclei
Nuclei at the neutron drip line (Z→25)
• Very large proton-neutron asymmetries
• Resonant excitation modes
• Neutron Decay
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