A dvanced GA mma T racking A rray
description
Transcript of A dvanced GA mma T racking A rray
AAdvanceddvanced GAGAmmamma TTrackingracking AArrayrray
Performance of an AGATA prototype detector estimated by Compton-imaging techniques
Francesco RecchiaINFN - Legnaro
on behalf of the AGATA collaboration
180 large volume 36-fold segmented Ge crystals packed in 60 triple-clusters
Digital electronics and sophisticated Pulse Shape Analysis algorithms
Operation of Ge detectors in position sensitive mode for -ray tracking
Efficiency: 43% (M=1) 28% (M=30)today’s arrays ~10% 5%
Peak/Total: 58% (M=1) 49% (M=30)today ~55% 40%
Angular Resolution: ~1º
FWHM (1 MeV, v/c=50%) ~ 6 keV today ~40 keV
Design values: 5 mm of position resolution assumed
Triple cluster
Rint = 23 cm
Rext = 32 cm
The -ray spectrometer AGATA
180 HPGe
Pulse Shape Analysisto decompose
recorded waves
Highly segmented HPGe detectors
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Identified interaction points
(x,y,z,E)i Reconstruction of scattering sequence from
Compton vertices
Digital electronicsto record and
process segment signals
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2
3
4
ReconstructedReconstructed
gamma-raysgamma-rays
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Ingredients of -ray tracking
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,10,46)
measured
(10,30,46)
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,10,46)
measuredcalculated
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,15,46)
measuredcalculated
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,20,46)
measuredcalculated
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,25,46)
measuredcalculated
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,30,46)
measuredcalculated
Result of Grid Searchalgorithm
Pulse Shape Analysis concept
B4 B5B3
C4 C5C3
CORE
A4 A5A3
C4
D4
E4 F4
A4
B4
x
y
z = 46 mm791 keV deposited in segment B4
(10,25,46)
measuredcalculated
A test-beam experiment has been performed to measure this parameter in realistic experimental conditions
Simulations suggest that the overall performance
depends on the attainable position resolution
The position resolution required for the AGATA detectors
Setup of the in-beam experiment
BEAM 48Ti 100 MeV
TARGET 48Ti + 2H 220 μg/cm2
Si detectorDSSSD
Thickness: 300 μm
32 rings, 64 sectors
AGATA symmetric triple-cluster
d(48Ti,49Ti)p
Symmetric triple cluster
Silicon detector
Digitizers:
30 XIA DGF 4c cards
40MHz 14 bit
experiment performed at IKP of Cologne
Doppler correction using PSA results
Full statistics usedFull statistics used
32 keV
Doppler correction using PSA results
Full statistics usedFull statistics used
32 keV
11 keV
Doppler correction using PSA results
Full statistics usedFull statistics used
PSA algorithm: Grid Search
32 keV
11 keV
4.8 keV4.8 keV
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3
4
5
6
7
8
9
0 1 2 3 4 5 6 7 8 9 10 11 12 13
position resolution FWHM [mm]
peak F
WH
M [keV]
Simulation vs Experiment
Grid Search
Recursive Subtraction
Matrix Method
Results obtained with different PSA
algorithm
Miniball Algorithm
Why Compton imaging?
15 days of beam-time to perform the test experiment
1 year of analysis PSA will be on-line
Need for a simpler procedure Need an prompt feed-back
from on-line analysis
Compton imaging
In-beam experiment: typical conditions
of future use
Compton imagingof a radioactive source inverse tracking
E1
E2
target
E1
E2
-source
Compton imaging performance
Error on Compton identification of source direction from:
Position resolution (axis) Energy resolution (scattering
angle) Compton profile
(scattering angle)
scattering angle [deg]
ang
ula
r er
ror
[deg
]
Imaging setup at LNL
AGATA prototype detector
TNT2 Digitizers: 4ch 14bit 100MHz
60Co source
Outline of analysis/simulation
Event selection
PSA
Position resolution
DAQ
Event selection
Smearing (position resolution)
Image formation
MC
Image formation
Comparison to simulation
E
E,pMC + E res + pos res Exp
MC + E resMC
≈
≈
Simple back-projections
Comparison to MC simulation
profile of experimental image
Monte Carlo + 5 mm position resolution
profile of experimental image
5.2
4.7
Experiment
[deg]
[d
eg]
[deg]
[d
eg]
pea
k F
WH
M[
deg
]p
eak
FW
HM
[d
eg]
position resolution FWHM[mm]
position resolution FWHM[mm]
CONCLUSIONS
Position resolution extracted by in-beam experiment and Compton imaging is 5 mm FWHM.
This value is in line with the design assumptions of the AGATA spectrometer, confirming the feasibility of -ray tracking.
AGATA will have a huge impact on nuclear structure studies (first phase of AGATA: LNL 2009…)
Possible applications of -ray tracking detectors to imaging.
Basic implementation of LMML
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620
Compton imaging application