development of an 8×8 array of labr3(ce) pixels with a...
TRANSCRIPT
Development of an 8×8 array of LaBr3(Ce) pixels with a multi-
anode PMT for a gaseous Compton gamma-ray camera
Shunsuke KUROSAWA K. Hattori, C. Ida, S. Iwaki, S. Kabuki, H. Kubo,
K. Miuchi, H. Nishimura, A. Takada, M. Takahashi, T. Tanimori, K. Ueno, Y. YanagidaA
Dept. of Physics, Graduate school of Science, Kyoto University, Kyoto, JapanAWorld Engineering System, Kyoto, Japan
NDIP-08 Palais des Congrès, Aix-les-Bains France, June 16, 2008
Contents
• Introduction– Compton gamma-ray Camera
• LaBr3 array • Compton Camera with LaBr3 array• Summary
Compton gamma camera
Reconstruct an incident gamma ray event by event
gaseous TPC(time projection chamber) :[containing μ-PIC(MPGD), GEM]--- energy and 3-D track of
a recoil electronScintillation camera:[ GSO (Ce) pixel array ]
--- energy and position of a scattered gamma ray
10cm
Scintillator
TPC
μ-PICGEM
Large FOV (~3str)Kinematical background rejection
by comparison of two α angles
This Camera is for Astronomy,medical imaging.
α
8×8 multi-anode PMT(MAPMT) HPK H8500
size: 52×52 mm2
effective area:49×49 mm2
anode pitch: 6.1 mm
GSO array (8×8 pixels)effective area:
49×49 mm2
pixel size:5.8×5.8×13mm2
pixel pitch: 6.1mmsame as the PMT
reflector: ESR© (3M)
Scintillator array camera
Resistor chainAll 100Ω
4ch readout with a resister chain
Energy resolution (FWHM)10.7 ± 1.0 % @ 662 keV
(GSO has a strong radiation hardness)
X, Y position
Energy
Charge-divisionmethod
Sum
preAMP. 64 anodesof PMT
4 ch output
Improvement of Angular ResolutionNow :Angular resolution (FWHM): 6.4°@ 662keV
Angular resolution of a Compton cameradepends on the energy resolution of scintillator
10.5 % 4.2°7% 3.1°5% 2.3°3% 2.1°
Sci. Ener. Res. @662keV
Com. AngularRes. @662keV
Doppler broadening (Ar) Zoglauer et al. (2003)
Ang
ular
reso
lutio
n (F
WH
M) [
degr
ee]
Scattered γE : ene.
Recoil e-
K: ene.
Scattering angle φ
α
Incident γΔφ Angular resolution
(ARM)
Calculation assuming1, no error of position of
Compton point2, energy Res. of TPC
: 30 % @ 22 keV
cosφ=1-mec2 K
(E+K) E
LaBr3(Ce) scintillator
Energy resolution measured with a single-anode PMT (SAPMT)(HPK R6231)
Excellent energy resolutionHigh light yield : 160 NaI%
[ cf. GSO(Ce) : 20 NaI% ]Fast decay time: ~20 nsechygroscopic
Loef et al., (2000)
Saint-Gobain BrilLanCe380
Size:φ38×38mm3
3.3 ± 0.1 %@ 662 keV
4.1 ±0.1 % @ 356 keV
GSOLaBr3 E-0.501±0.002
Assembly of LaBr3(Ce) array
6.1 mm pitch
Effective area : 49 × 49 mm2
(=PMT photocathode)Glass window : Quartz (t 2.3 mm)
Hermetic package : Aluminum ( t 0.5 mm )
Saint-Gobain BrilLanCe380
Size:φ38×38mm3
We cut 5.8×5.8×15.0mm3 pixels out of two φ38×38 mm3
LaBr3 crystals and assembled an 8×8 array by our technique.
54mm
20mm1/2 attenuation length
@662keV LaBr3 (Ce): 18 mm
Performance of each pixelTo estimate the performance without the effect of gain-uniformity (∼3) among 64 anodes of MAPMT (H8500)
Single-anode PMTHPK R6236 (2-inch square )
LaBr3 array
7cm133Ba
irradiation of collimated gamma rays to a pixel one by one
φ2mm
Energy resolution (FWHM)@ 356 keVAve. ± RMS = 5.5 ± 0.7 %
Map of energy Res. of 8 × 8 pixels
Energy resolution (FW
HM
) [%]
4ch readout with H8500LaBr3 array MAPMT HPK H8500
Resister chain
Readout system is the same as the GSO array
Image and energy spectrumFlood field irradiation image by Charge-division method
φ38×38mm3
monolithiccrystal 8x8 pixel
array
Energy spectrum(133Ba)
(sum of all pixels)
137Cs
Energy resolution (FWHM) of each pixel @ 662 keV (137Cs)
Ave. ± RMS :5.8 ± 0.9%
LaBr36×6×15 mm3 8×8 array
Energy R
esolution(FW
HM
) @ 662 keV
[%]
Ave. ± RMS :10.8 ± 1.0%
GSO 6×6×13 mm3 8×8 array
Energy Resolution (2)
LaBr36×6×15 mm3 8×8 array: FWHM(%)=(5.7±0.4)
×(E/662keV)-0.53±0.01
LaBr3array
GSO 6×6×13 mm3 8×8 array: FWHM(%)=(10.4±0.3)
×(E/662keV)-0.51±0.01
LaBr3φ38×38mm3
crystal
GSOarray
Improved by factor ~2 Worsened by factor ~2
LaBr3array
Setup of Compton cameraGaseous TPC(8 ×8 LaBr3
pixels) 2×2
110mm
10cm
Drift cage
GEM
μ-PIC
containing Ar+C2H6 1atm
LaBr3 TPC source
50mm 200mm
γe-
γ
3-D electron tracking
500keV
Performance of Compton camera
Source 131I (364keV)3cm
3cm cube
LaBr3
LaBr3 TPC source
50mm 200mm
γe-
γ
with LaBr3 arraywith GSO array
Improvement of the angular resolutionA
ngul
ar re
solu
tion
(FW
HM
) [de
gree
]
Angular resolution(FWHM) @662 keV[degree]
6.4±0.2 (GSO)
4.2±0.3 (LaBr3)
With GSO array
With LaBr3 arrayimproved
summary• We assembled an 8×8 LaBr3 pixel array in order to improve
the angular resolution of Compton Camera.– Pixel size : 5.8 ×5.8 ×15 mm3
– Pixel pitch: 6.1mm (the same as that of MAPMT H8500)– Package size : 54 ×54 ×20 mm3 (compact)
• Dynamic rage: 80 – 1000 keV• Energy resolution of the array with MAPMT (FWHM、
@662keV)– GSO array 10.7 ± 1.0 %– LaBr3 array 5.8 ± 0.9 %
• Angular resolution of Compton camera (FWHM, @ 662 keV)– With GSO array 6.4±0.2 deg.– With LaBr3 array 4.2±0.3 deg. (improved)
• Future works– We assemble more LaBr3 arrays for expanding the effective
area of Compton camera. – Individual readout system of all anode channels.
Fin
Scintillator
very strong
strong
strong
strong
weak
very weak
very weak
Radiation Hardness
No
Very strong
No
No
No
Weak
Strong
Hydroscopic
1.6250.55.3LaBr3
0.4-0.75400.877.4LSO
0.07-0.123000.927.13BGO
0.3-0.45400.384.45YSO
0.18~600.706.71GSO
0.8510500.444.53CsI(Tl)
12300.343.67NaI(Tl)
Light output(Relative)
Decay time constant(ns)
Absorption coefficient (cm-1)@511keV
Density(g/cm3
)
large
large
large
fast
fast
fast
Scintillator 2LaBr3 LaCl3 LuI2 NaI (Tl)
Density 5.29 3.86 5.6 3.67
Light OutputPhotons / MeV
63,000 49,000 >50,000 39,000
Energy Res. @662keV
3% 4% 10% 7%
Peak λnm 358-385 330-352 475 425
Fast Decay (ns)
25 25 23 230
Uniformity of material(φ38mm t38mm Saint-Gobain)
PMT side
0mm
10mm
25mm
35mm
d4
d5
d6
d1
d2
d3
O1
O3
O5
O7
side viewPMT side
0mm
10mm
25mm
35mm
d4
d5
d6
d1
d2
d3
O1
O3
O5
O7
side view Uni. Of l.o. : no problem
1.02
4.3%(FWHM)
1.006(av)±0.005(rms)
4.08(av)±0.07(rms) %
3.9%
Uni. Of l.o. : no problem
9mm18mm
8
I1
I7
C9mm
O 1
O2
O3
O4O6
O7
O8
O5
I3
I5
Top view
9mm18mm
8
I1
I7
C9mm
O 1
O2
O3
O4O6
O7
O8
O5
I3
I5
Top view
0.99E
nerg
y re
s. @
356k
eV
Map of anode gain of MAPMT
Max. gain / min. gain=2.4
Hamamatsu H8500
Charge division method
x = (a + b - c - d) / (a + b + c + d)y = (a + c - b -d) / (a + b + c + d)E = a + b + c + d
#n1Peak-to-valley ratio : 13.5 (平均値)
#2
#3
#4Peak-to-valley ratio : 13.3 (平均値)
1 2
3
Variety = 20 %
5.8 ±0.8 % 5.8 ±0.9 %
6.4 ±1.2 % 6.0 ±0.8 %
Doppler broadening
Zoglauer et al. 2003
TPC : 10x10x15cm3
(gas: Xe+Ar+C2H6 1atm)Scintillator: GSO
137Cs全面照射
BGD
7.5×10-4Hz/cm3
138La 1435keV
Gaseous TPC
size:10 × 10 × 10 cm3
gas:Ar(90%)+C2H4(10%)1atm (sealing)
electric field :0.4 kV/cm (drift) 2.5 kV/cm
(GEM ~ μ-PIC)
drift: FPGA 100MHz clock
10cm
400μm
μ-PIC (micro pixel chamber)
2-dimensional imaging gaseous detector
μ-PIC
GEM
Drift cage
105
104
103
gas
gain
440 460 480 500 520HV [V]
Gas gain ~35000
FWHM(%)=(29.5 ± 0.8 )×(E/22.2keV)-0.508 ±0.008
Ene
rgy
Res
. (FW
HM
)[%
]
2 3 10 20 30energy [keV]
μ-PIC(Micro Pixel Chamber)
10cm
• 2-D readout(~65000pixels)• 10cm×10cm• Max gain ~15000• Energy res.
30% @ 5.9keV (100cm2)• Gas gain~6000
stable operation for morethan 1 month
• Position res. (~120μm)
probe
banana plug
Xe:C2 H6 = 7:3
55Fe spectrum10×10cm2
Ar-esc
MnKα
FWHM ~33%
Uniformity : σ ~ 5%
μ-PIC as a X-ray detector
GEM (Gas Electron Multiplier) Sauli (1997)
Set up of Compton camera10cm
source Gaseous TPC
μ-PIC
LaBr3 array+ multi-anode PMT
20cm 5cm
Scint.TPC Scint.+TPC
TPC Scinti.γ
e-
(Ene. of recoil electron) + (Ene. Scat. gamma) = (Ene. Of inc
GSOLaBr3
0 200400
Energy[keV]
133Ba
0 30 60 90Energy [keV]
0 200 400Energy [keV]
Cou
nts
(a. u
.)
Cou
nts
(a. u
.)
Cou
nts
(a. u
.)
Energy Spectrum
GSOLaBr3
Improvement of the angular resolutionA
ngul
ar re
solu
tion
(FW
HM
) [de
gree
]
Angular resolution(FWHM) @662 keV[degree]
6.4±0.2 (GSO)
4.2±0.3 (LaBr3)
With GSO array
With LaBr3 arrayimproved
Cf. Angular resolution @ 662 keVSi/Ge Hybrid ~ 3.5 deg. Burks et al. (2005)
Scattered γE : ene.
Recoil e-
K: ene.
Scattering angle φ
α
Incident γΔφ Angular resolution
(ARM)
er rr⋅=αcos