Advanced gamma – ray spectroscopy with AGATA
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Transcript of Advanced gamma – ray spectroscopy with AGATA
Advanced Gamma–Ray Spectroscopy
Techniques with the AGATA Segmented
DetectorsCălin A. Ur*
for the AGATA CollaborationINFN – Sezione di Padova
*On leave from IFIN–HH Bucharest
Layout
01/02/2010 2ELI NP Workshop Bucharest
• 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
Extreme Experimental Conditions
01/02/2010 3ELI NP Workshop Bucharest
• Low intensity• High backgrounds• Large Doppler
broadening• High counting rates• High -ray multiplicities
High efficiencyHigh sensitivityHigh throughputAncillary detectors
FAIRSPIRAL2SPESREX-ISOLDEEURISOLHI-SIB
Need instrumentation
Extreme Experimental Conditions
01/02/2010 4ELI NP Workshop Bucharest
• Low intensity• High backgrounds• Large Doppler
broadening• High counting rates• High -ray multiplicities
High efficiencyHigh sensitivityHigh throughputAncillary detectors
FAIRSPIRAL2SPESREX-ISOLDEEURISOLHI-SIBELI ?
Need instrumentation
The New Concept of Tracking Arrays
01/02/2010 5ELI NP Workshop Bucharest
Tracking Arrays based onPosition Sensitive Ge Detectors
Gamma Arrays based on Compton Suppressed Spectrometers
~ 50 — 25 % ( M=1 — M=30)
~ 10 — 7 % ( M=1 — M=30)
GAMMASPHEREEUROBALL GRETAAGATA
AC
AC
Comptonrejected
Full energyaccepted
Analogue vs Digital Electronics
01/02/2010 6ELI NP Workshop Bucharest
Detector(Germaniu
m)
Shaping Amplifier
CFD DAQ
E
t
FADC
MWD
NSR
Filters
DAQ
E
t
ADC
TDC
PSA
Trac
king
E
t
x,y,z
E
t
Present Arrays
AGATA
Segment Detector Array
Detector(Germaniu
m)
Ingredients of Gamma–Ray Tracking
01/02/2010 7ELI NP Workshop Bucharest
Pulse Shape Analysisto decompose
recorded waves
Highly segmented
HPGe detectors
··
Reconstruction of tracks evaluating permutations
of interaction points
Digital electronicsto record and
process segment signals
1
23
4
Reconstructed
gamma-rays
Th. Kröll, NIM A 463 (2001) 227
Position Determination – PSA
01/02/2010 8ELI NP Workshop Bucharest
FEM-modelof detector
Calculateweighting
fields
Calculation of the signals induced on the contacts using the weighting field method
transient signals
net charge signals
Pulse Shape Analysis Concept
01/02/2010 9ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,10,46)
measured
(10,30,46)
Pulse Shape Analysis Concept
01/02/2010 10ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,10,46)
measuredcalculated
Pulse Shape Analysis Concept
01/02/2010 11ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,15,46)
measuredcalculated
Pulse Shape Analysis Concept
01/02/2010 12ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,20,46)
measuredcalculated
Pulse Shape Analysis Concept
01/02/2010 13ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,25,46)
measuredcalculated
Pulse Shape Analysis Concept
01/02/2010 14ELI NP Workshop Bucharest
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,30,46)
measuredcalculated
Pulse Shape Analysis Concept
01/02/2010 15ELI NP Workshop Bucharest
Result of Grid Search
algorithmR. VenturelliB4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm
791 keV deposited in segment B4
(10,25,46)
measuredcalculated
Interaction/Reconstruction Algorithms
01/02/2010 16ELI NP Workshop Bucharest
~ 100 keV ~1 MeV ~ 10 MeV -ray energy Photoelectric Compton Scattering Pair Production
Algorithms: ClusterTracking, FuzzyTracking, BackTracking, …Reconstruction efficiency limited by Position resolution and Compton profile.
Probability ofinteraction depth
Isolated hits
cosθ1cm
E1
EE
20
γ
γγ'
Angle/Energy
Pattern of hitsE1st = E – 2 mc2
Pulse Shape Analysis Concept
01/02/2010 17ELI NP Workshop Bucharest
Idealized configuration to determinemaximum attainable performance.
Ri = 15 cmRo = 24 cm230 kg of Ge
Events simulated using GEANT4Response of shell at 1.33 MeV:ph = 70% P/T = 77%Reconstruction by Cluster-TrackingPacking Distance: 5 mmPosition Resolution: 5 mm (at 100 keV)1.33 MeV
M = 1
M = 30
ph (%) 65 36P/T(%) 85 60
27 gammas detected -- 23 in photopeak16 reconstructed -- 14 in photopeak
E = 1.33 MeVM = 30
A high multiplicity event
D. Bazzacco
Possible Array Configurations
01/02/2010 18ELI NP Workshop Bucharest
120 crystals
180 crystals
Configuration 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 81.6Ge weight (kg) 232 225 230 363Centre to Ge (cm) 19.7 18 18.5 23.5Electronics channels 4440 4440 4440 6660
Eff. at M = 1 (%) 32.9 36.9 36.4 43.3Eff. at M = 30 (%) 20.5 22.0 22.1 28.1P/T at M = 1 (%) 52.9 53.0 51.8 58.2P/T at M = 30 (%) 44.9 43.7 43.4 49.1
A180 is AGATA’s choice
GRETA is for A120C4
The Advanced GAmma Tracking Array
01/02/2010 19ELI NP Workshop Bucharest
Requirementsefficiency, energy resolution, dynamic range, angular resolution, timing, counting rate, modularity, angular
coverage, inner space
Quantity Specified for Target Value
Photo-peak efficiency (ph)
Eγ = 1 MeV, Mγ = 1, < 0.5Eγ = 1 MeV, Mγ = 30, < 0.5Eγ = 10 MeV, Mγ = 1
50 %25 %10 %
Peak-to-total ratio (P/T)Eγ = 1 MeV, Mγ = 1Eγ = 1 MeV, Mγ = 30
60 - 70 %40 - 50 %
Angular resolution () E/E < 1% better than 1
Maximum event ratesMγ = 1Mγ = 30
3 MHz300 kHz
Inner space for ancillaries > 170 mm
Construction of the AGATA Array
01/02/2010 20ELI NP Workshop Bucharest
Total weight of the 60 clusters of the AGATA-180 configuration ~2.5 tonsMounted on a self-supporting structure
Ge crystals:Hexaconical shape90-100 mm long80 mm max diameter36 segmentsAl encapsulation: 0.4 mm spacing 0.8 mm thickness
Distance between faces of crystals: in same cluster ~2.5 mm in adjacent clusters ~9.0 mm
Triple clusters: 3 encapsulated crystalsAl end-cap: 2.0 mm spacing 1.0 mm thickness111 cold FET preamplifiers
Asymmetric AGATA Triple Cryostat
01/02/2010 21ELI NP Workshop Bucharest
Challenges: - mechanical precision - heat development, LN2 consumption - microphonics - noise, high frequencies
- integration of 111 high resolution spectroscopy channels- cold FET technology for all signals
@1.3 MeV@ 60 keV
Core2.10 keV @ 1.3 MeV1.20 keV @ 60 keV
Electronics and DAQ
22
Fully synchronous system with global100 MHz clock and time-stampdistribution (GTS)
GTS …detector
Preamps
Digitizers
detector
Preamps
Digitizers
Localprocessing
Localprocessing
7.4 GB/s/det
PSA PSA
5 MB/s/det
100 MB/s/det
DigitalDigital
preamplifier
preamplifier
On line…Storage …
Tracking
EventBuilder
Local processing triggered by Ge commoncontact. Determine energy and isolate ~ 600 ns of signal around rise-time
Digitizers: 100 Ms/s, 14 bitOptical fiber read-out of full datastream to pre-processing electronics
Buffers of time-stamped local events sentto PSA to extract position of interactionsTrigger-less system. Global trigger possible.
Global event builder and software trigger
On-line gamma-ray tracking
Control and storage (~1 TB/year), …
clk
@ 50 kHz
01/02/2010 ELI NP Workshop Bucharest
The Phases of AGATA 1
2301/02/2010 ELI NP Workshop Bucharest
5 Clusters5 ClustersDemonstratDemonstrat
oror
Our days
Main issue is Doppler correction capability coupling to beam and recoil tracking devices Improve resolution at higher recoil
velocityExtend spectroscopy to more exotic nuclei
Peak efficiency3 – 8 % @ M = 12 – 4 % @ M = 30
The Phases of AGATA 2
2401/02/2010 ELI NP Workshop Bucharest
The first “real” tracking array
To be used at FAIR-HISPEC, SPIRAL2, SPES, …
15 Clusters 15 Clusters 11
0
5
10
15
20
25
30
35
40
45
50
1 2
Effi
cien
cy (%
)
Solid Angle (%)
Efficiency M = 1
Efficiency M = 10
Efficiency M = 20
Efficiency M = 30
= 0 = 0.5
Near future
Recoil velocity
The Phases of AGATA 3
2501/02/2010 ELI NP Workshop Bucharest
Efficient as a 120 ball (20% at high multiplicity)
Ideal for FAIR and EURISOL
45 Clusters45 Clusters33
Far future
The Phases of AGATA 4
2601/02/2010 ELI NP Workshop Bucharest
Full ball / full performance
Ideal to study extreme deformations and the most exotic nuclear species
60 Clusters60 Clusters44
Remote future
The AGATA Demonstrator
2701/02/2010 ELI NP Workshop Bucharest
Objective of the R&D phase 2003-2008
5 asymmetric triple-clusters36-fold segmented crystals540 segments555 digital-channelsEff. 3 – 7 % @ M = 1Eff. 2 – 4 % @ M = 30
Full ACQ online PSA and –ray trackingCost ~5 M€
Present status3 asymmetric triple-clusters mounted&tested at INFN LN Legnaro +1 in deliveryUndergoing commissioning runs detectors, DAQ, PSA, onlinePhysics campaign to start in ~1 month
First in–beam Test at LNL
2801/02/2010 ELI NP Workshop Bucharest
• 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
Doppler Broadening and Position Res.
2901/02/2010 ELI NP Workshop Bucharest
Position resolution
Angular resolution
Energy resolution
BeamRecoil
ray
Doppler Broadening and Position Res.
3001/02/2010 ELI NP Workshop Bucharest
12.5 keV40K1823
keV ~ 5%
full detectorsegments (17.7 keV)PSA+tracking
Full optimization and analysis – 1 month
onlineour target
Compton Imaging
3101/02/2010 ELI NP Workshop Bucharest
• In-beam experiment– given the position
of the target we track the rays
• Compton imagingof a radioactive source– inverse tracking –
from the first 2 interaction points get the position of the source
E1 E2
target
E1 E2
-source
Compton scattering – a tool for testing the position resolution
ray
ray
Compton scattering
F. Recchia
Principles of Compton Imaging
3201/02/2010 ELI NP Workshop Bucharest
[d
eg]
20
111cos cmEE
Compton Imaging Performance
3301/02/2010 ELI NP Workshop Bucharest
Sources of error in the identification
of the source direction:
• Position resolution (axis)• Energy resolution (scattering
angle)• Compton profile (scattering
angle)
scattering angle [deg]
angu
lar e
rror [
deg]
Experimental Setup at LNL
3401/02/2010 ELI NP Workshop Bucharest
Digital DAQ system provided by IFIN – HH Bucharest
• 10 x TNT2 NIM Digitizer boards from CAEN with 4ch 14bit /100MHz
AGATA prototype detector(one symmetric capsule)
60Co source
Comparison with MC Simulations
3501/02/2010 ELI NP Workshop Bucharest
profile of experimental imageMonte Carlo +
5 mm position resolution
profile of experimental image
5.2
4.7
Experiment
[d
eg]
[deg]
[d
eg]
peak
FW
HM[
deg]
peak
FW
HM[
deg]
position resolution FWHM[mm]
position resolution FWHM[mm]
After PSAProjections
MC
MC
Gamma Background Rejection
3601/02/2010 ELI NP Workshop Bucharest
characterize the capability of the AGATA detectors to discriminate different gamma source locations using Compton imaging algorithmExperimental Setup: 3 –ray sources 60Co, 152Eu and 137Cs
their positions simulate the beam-dump, the beam line and the target
M. Doncel & F. Recchia
Results
3701/02/2010 ELI NP Workshop Bucharest
b)
a)
c)
Spectra of the gamma radiationassigned to each source positionwith 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 E = 344 keV
E = 661 keV
E1 = 1173 keVE2 = 1332 keV
Outlook
3801/02/2010 ELI NP Workshop Bucharest
To exploit the present and future facilities fully and most efficiently, advanced instrumentation and detection equipment is required – NuPECC recommendationThe 4-array of highly segmented Ge detectors AGATA for -ray detection and tracking is part of this effortFirst 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 -ray trackingAGATA 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?
The AGATA Collaboration
3901/02/2010 ELI NP Workshop Bucharest
Bulgaria: SofiaDenmark: CopenhagenFinland: JyväskyläFrance: GANIL, Lyon, Orsay, Saclay, StrasbourgGermany: Berlin, Bonn, GSI, Darmstadt, Jülich, Köln,
MünchenHungary: DebrecenItaly: Padova, Milano, LNL, Firenze, Camerino, Napoli,
GenovaPoland: Krakow, Swierk, WarsawRomania: BucharestSweden: Lund, Stockholm, UppsalaTurkey: Ankara, IstanbulUK: Daresbury, Brighton, Keele, Liverpool,
Manchester, Paisley, Surrey, York
Outlook
4001/02/2010 ELI NP Workshop Bucharest
First in–beam test with STC
4101/02/2010 ELI NP Workshop Bucharest
32 keV
11 keV
4.8 keV4.8 keV
Symmetric triple cluster
Silicon detector
experiment performed at IKP of Cologne
Position resolution extracted through a comparison to detailed Monte Carlo simulations (FWHM vs. pos. resolution)
~5.2 mm
New Challenges from the RIB Facilities
01/02/2010 42ELI NP Workshop Bucharest
Neutron rich heavy nuclei (N/Z → 2)• Large neutron skins (r-r→ 1fm)• Shell quenching
Nuclei at the neutron drip line (Z→25)• Very large proton-neutron asymmetries• Resonant excitation modes• Neutron Decay
Nuclear shapes• Exotic shapes and isomers • Coexistence and transitions
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 Astrophysics• Properties of r and rp process nuclei