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