Development of anElectron-Tracking Compton Camera

using CF4 gas at high pressurefor improved detection efficiency

Michiaki TakahashiN. Higashi, S. Iwaki, S. Kabuki, H. Kubo, S. Kurosawa,

K. Miuchi, K. Nakamura, J. D. Parker, T. Sawano, A. TakadaA, T. Tanimori, K. Taniue, and K. Ueno

Dept. of Physics, Graduate school of Science, Kyoto University, Kyoto, Japan

AISAS/JAXA, Kanagawa, JapanThe Twelfth Vienna Conference on Instrumentation, Vienna, Austria

20 February 2010

Outline

・ Introduction Electron-Tracking Compton Camera (ETCC) Medical imaging / MeV gamma-ray astronomy・　 Optimization of gas mixture・　 Operation at high pressure・　 Summary

Electron-Tracking Compton Camera (ETCC)

μTPC (Time Projection Chamber ）--- 3D track and energy of Compton-recoil electron Scintillation camera--- position and energy of scattered gamma ray

Scintillator

μPICGEM

e-

B26 K. Ueno, A22 S. Kurosawa

2 events１ 2 3

5 10 100

Determination of direction and energy of each incident gamma ray Large FOV ( 3 sr)

10 cm

400 m pitch

anodecathode

Proton

10cm

Electron

Example of 3D track

Electricfield

TPC (Time Projection Chamber)for 3D electron track

GEM (Gas Electron Multiplier) (F. Sauli (1997))+ μPIC (micro PIxel Chamber) 2D readout micro pattern gaseous detector 2D readout + Drift time 3D track

Prototype TPC size : 10×10×10 cm3

Gas : Ar/C2H6 (90:10) at 1 atm, sealedPosition resolution : 150 m (1D)Stable gas gain : 30000 (PIC : 3000, GEM : 10)

GSO and LaBr3 Scintillation Cameras

GSO 8×8 Pixel 13 mm 6 mm

15 x 15 cm2 Camera(GSO or LaBr3 + Multi anode PMT (H8500, HPK))

• Number of pixels: 576• Pixel size 6×6×13 mm3 (GSO) 6×6×15 or 20 mm3 (LaBr3)• GSO Energy resolution :10.0 % (@662keV, FWHM)• LaBr3 Energy resolution: 6.5% (@662keV, FWHM)• Position resolution: 6mm

Black :GSORed : LaBr3

15 cm

5 cm

MeV gamma-ray camera projects

Astronomy : Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment (SMILE)

1. SMILE-I (2006, launched)• Operation test of ETCC @35 km• Measurement of diffuse cosmic and atmospheric gamma rays ( 400 photons) 4 hours

2. SMILE-II (2011)• Observation of Crab Nebula or Cygnus X-1 3 hours

Medical : Advantage point: wide energy dynamic range (300 – 3000 keV) and wide FOV (SPECT < 300 keV, PET 511 keV) 1. Multi RI Tracer Imaging --- The development of new RI drugs 2. Proton Therapy --- Real time monitor of prompt gamma rays to measure Bragg-peak position

Scinti : LaBr3

Scinti : GSO

Energy window : ±10% 1004 1228 keV

Examples of Medical ImagingZn-65-Porphyrin imaging (1116 keV) Porphyrin was accumulated in RGK-36 which is the tumor of rat stomach cancer.

γ

60cm

180cm

365 keV(Tumor)

511keV(Brown fat cell)

Scinti : LaBr3

2 sources imaging

ETCC for medical use

Activity : 0.16 MBqTime : 110.5 hoursEvents : 173 events

Scintillator

TPC

Time : 6 hours

ETCC/CT

ETCC/CTSpatial resolution 10 mm (FWHM)

Improvement of detection efficiency

• Optimization of gas• Operation at high pressure

Increase detection area• Multi-head camera (10×10×10 cm3×2,3,…) • Developing a large size ETCC (30×30×30 cm3)

For High Sensitivity

2 times better thanour prototypes

Demerit of CF 4 gas Low gas gain isoC4H10 gas (penning effect)

High dependence of drift velocity on electric field 　　　　　　　　　　　　　　　　　　　　　　　 worse

position resolution ?

Selection of gas sealed in TPC

Merit of CF 4 gas

Small diffusion better position resolution (for TPC) better angular resolution (for ETCC) low Z (C : Z=6, F : Z=9) and 42 electrons in one molecule Compton scattering is dominant higher efficiency (for ETCC)

Ar/C2H6 (90:10) CF4 gas mixture

Drift CageDrift Cage

10 cm10 cm 10 cm

Optimize the gas mixture

Electronics

TPC

source

GEM (SciEnergy)

PIC

Gas Ar/C2H6 (90:10) Ar CF4

isoC4H10

Measurement1.Gas Gain2.Position Resolution

Requirements : High CF4 ratio

Gas Gain 20,000

10 cm

CF4 45%

CF4 50%

Improved by more than 2by introducing isoC4H10

This gasThis gas

GEM = 340V The other GEM = 400V

CF4 20%CF4 30% CF4 40%

Gas Gain at 1 atm Penning effect of isoC4H10

= 162 m

D = 81 m/cm1/2

= 162 m

D = 81 m/cm1/2

Ar/CF4/isoC4H10 (54:40:6)

muon tracks

= 156 m

D = 175 m/cm1/2

= 156 m

D = 175 m/cm1/2

Better by factor 2

22detector

2 )()( lDl l : Drift lengthD : Diffusion Constantl : Drift lengthD : Diffusion Constant

Position Resolution

Ar/C2H6 (90:10))

2( detector

Ar/C2H6 (90:10) at 1 atm

Ar/C2H6 (90:10) at 2 atm

Ar/CF4/isoC4H10 (54:40:6) at 1 atm

Ar/CF4/isoC4H10 (54:40:6) at 1.4 atm

Measurement1.Gas Gain2.Drift Velocity3.Position Resolution4.Energy Resolution

High Pressure100 mm

2 mm

100 mt GEM

2 mm

100 mm 50 mt GEMPIC

Drift Plane (Al Mylar)

Electronics

TPC

source

Gas Gain

Upper GEM = 350VLower GEM = 250V

Upper GEM = 460VLower GEM = 360V

Upper GEM = 500VLower GEM = 380V

Upper GEM = 610VLower GEM = 450V

Lower gas gain

Drift Velocity

Difference betweensimulation andmeasurementis smaller than 10%

Position Resolution

Ar/C2H6 (90:10)at 1 atm

Ar/C2H6 (90:10)at 2 atm

Ar/CF4/isoC4H10 (54:40:6)at 1 atm

Ar/CF4/isoC4H10 (54:40:6)　　　 at 1.4 atm

= 332 m, D = 246 m/cm1/2 = 302 m, D = 204 m/cm1/2

= 378 m, D = 147 m/cm1/2 = 330 m, D = 128 m/cm1/2

Better by factor 2Better by factor 1.6

Energy Resolution31 keV X-ray from 133Ba (31 keV)

Ar/C2H6 (90:10) at 1 atm Ar/C2H6 (90:10) at 2 atm

Ar/CF4/isoC4H10 (54:40:6) at 1 atm Ar/CF4/isoC4H10 (54:40:6) at 1.4 atm

43.8% (FWHM) @31 keV 53.1% (FWHM) @31 keV

56.1% (FWHM) @31 keV 60.0% (FWHM) @31 keV

Worse than prototype

Imaging with ETCCgamma-ray from 133Ba (356 keV, 800 kBq)

Electronics

TPC

sourceGSO Scintillation Camera

Measurement1. Efficiency2. Angular resolution (ARM

and SPD)

15 cm

ARM : Angular Resolution MeasureSPD : Scatter Plane Deviation

Efficiency and Angular Resolution (133Ba 356 keV)Gas Pressure Efficiency ARM (FWHM) SPD (FWHM)

Ar/C2H6 (90:10) 1 atm 1.81×10-5 10.4° 114.8°Ar/C2H6 (90:10) 2 atm 3.55×10-5 11.1° 105.1°

Ar/CF4/isoC4H10 (54:40:6) 1 atm 2.44×10-5 11.7° 117.9°Ar/CF4/isoC4H10 (54:40:6) 1.4 atm 3.51×10-5 11.2° 119.1°

AR

M (

FWH

M)

[degre

e]

10

1

50

5

SMILE-I 2006(Xe + GSO)

Ar/C2H6 TPC + GSO scintillatorthe highest spec.

This Work (GSO)

Ar/CF4/isoC4H10 (54:40:6)at 1.4 atm

Imaging of 133Ba15 cm away from top of

TPC

better byfactor 1.94

Ar/C2H6 TPC+ LaBr3 scintillator

Summary• In order to improve the efficiency of the ETCC, we have

optimized the gas mixture and pressure sealed in the TPC.• The highest ratio of CF4 gas with steady gas gain of 20,000

is Ar/CF4/isoC4H10 (54:40:6).

• The diffusion constant of Ar/CF4/isoC4H10 (54:40:6) is

2 times better than that of Ar/C2H6 (90:10), so the position resolution is improved.

• The efficiency for the ETCC using Ar/CF4/isoC4H10 (54:40:6) at 1.4 atm is 2 times higher than that using Ar/C2H6 (90:10) at 1 atm, and those ARMs are comparable (11 at 356 keV (FWHM)).

Thank youfor your attention

Vs. Conventional Compton Camera Advanced Conventional

•Reconstruction : circle •Direction error region : donut

DO NOT measurethe track of a Recoil electron

150 events

600 events

-15-15

15

15

X [cm]

Y [

cm]

-15-15

15X [cm]

15

Y [

cm]

137Cs(1MBq)2, Classical Compton137Cs(1MBq)2, Advanced Compton

Measure the 3-D track of a Recoil electron

•Reconstruction : point •Direction error region: arc

COMPTELOur ETCC

Position-Sensitive Scintillation Camera

13mm6 mm

5cmMulti-anodePhoto Multiplier Tube (PMT)HPK H8500 8x8 anodes

GSO(Ce) 8x8 pixelsPixel size: 6x6x13mm3

5cm

-0.8 -0.4 0 0.4 0.8 X-position (a. u.)

0.8

0.4

0

-0.4

-0.8

Y-po

sitio

n (a

. u) 500

400

300

200

100

0

Coun

ts (a

. u.)

2-D image in flood-field irradiation

137Cs

Dynamic energy range: 0.08 -1 MeVEng. Resolution: 10.5 % @662 keV

Assembly of LaBr3(Ce) array

6.1 mm pitch

Using our technique, we assembled an 88 array.

54mm

20mm

(=multi-anode PMT H8500 anode pitch)

GSOarray

LaBr3 array

LaBr3 FWHM(%)=

(5.70.4) (E/662keV)-0.530.01

GSO FWHM(%)=

(10.40.3)(E/662keV)-0.510.01LaBr3 ： hygroscopic

Hermetic package

GSO monolithicLaBr3 monolithic

133Ba

E/E = 4.1 0.1 % @ 356 keV (FWHM)

Angular Res. Simulation including TPC

Scattered E : energy

Recoil e-

K: energy

Scattering angle φ

Incident φ Angular resolution (ARM)

Calculated assuming1, no error in position of Compton point

2, energy Res. of TPC : 30 % @ 22 keVEng. Res. (FWHM) of LaBr3(Ce) :

~ 3 % @ 662 keV Loef et al. (2001)

Doppler broadening (Ar) Zoglauer et al. (2003)

Ang

ular

res

olut

ion

(FW

HM

) [d

egre

e]

10.5 % 4.27% 3.15% 2.33% 2.1

Sci. Eng. Res. @662keV

ETCC. AngularRes. @662keV(FWHM)

Energy Dynamic Range

Ce-139

Cr- 51

Ba-133

I-131

Au-198

Na- 22

F-18

Cu- 64

Cs-137

Mn-54

Fe- 59

Zn- 65

Co- 60

Energy [keV]

167 320 354 364 412 511, 1275

511 511 662 835 1095, 1292

1116 1173, 1333

Energy dynamic range : 167 – 1333 keV.

Measured sources

SPECT PET

26

Spatial resolution vs. Energy

Goal : Same resolution as human PET @ 511keV

Spatial Resolution

27

I-131-MIBG & F-18-FDG imaging (365 & 511 keV)

PET/SPECT/CT

Rainbow ： PETOrange ： SPECT

Rainbow ： 511keVOrange ： 365keV

PC12

Brown fat cell

PC12

Brown fat cell

6cm

Dept. of Bioanalysis, Kyoto UniversityH. Kimura, H. Amano and H. Saji

Scinti : LaBr3

Zn-65 mouse imaging

Measurement after dissectionLiver :0.04 MBqSpleen :0.02Pancreas:0.02Heart :0.02Stomach : 0.01Kidney : 0.00Intestinal:0.11Brain :0.02Other :0.79BG :0.03

Mouse Zn-65 imaging

Energy : 1116keV activity : 1.4MBq obs. time : 2784 min Events : 629 events

3x3 LaBr3 Install to 10cm-ETCC

Zn is a good tracer for diabetes

All kinds of experiment gas (45 types)No

.Gas

1 CF4/isoC4H10 (95:5)

2 CF4/isoC4H10 (90:10)

3 CF4/isoC4H10 (80:20)

4 Ar/C2H6 (90:10)

5 Ar/C2H6/CF4 (72:8:10)

6 Ar/C2H6/CF4/isoC4H10 (69.3:7.7:20:3)

7 Ar/C2H6/CF4 (63:7:30)

8 Ar/C2H6/CF4 (54:6:40)

9 Ar/C2H6/CF4 (45:5:50)

10 Ar/C2H6/CF4/isoC4H10 (42.3:4.7:50:3)

11 Ar/C2H6/CF4 (27:3:70)

12 Ar/CF4/isoC4H10 (95:3:2)

13 Ar/isoC4H10 (90:10)

14 Ar/CF4 (90:10)

15 Ar/CF4 (80:20)

No.

Gas

31 Ar/CF4/isoC4H10 (64:30:6)

32 Ar/CF4/isoC4H10 (63:30:7)

33 Ar/CF4/isoC4H10 (56:40:4)

34 Ar/CF4/isoC4H10 (55:40:5)

35 Ar/CF4/isoC4H10 (54:40:6)

36 Ar/CF4/isoC4H10 (53:40:7)

37 Ar/CF4/isoC4H10 (52:40:8)

38 Ar/CF4/isoC4H10 (49:45:6)

39 Ar/CF4/isoC4H10 (47:50:3)

40 Ar/CF4/isoC4H10 (46:50:4)

41 Ar/CF4/isoC4H10 (45:50:5)

42 Ar/CF4/isoC4H10 (44:50:6)

43 Ar/CF4/isoC4H10 (43:50:7)

44 Ar/CF4/isoC4H10 (42:50:8)

45 Ar/CF4/isoC4H10 (40:50:10)

No.

Gas

16 Ar/CF4/isoC4H10 (78:20:2)

17 Ar/CF4/isoC4H10 (77:20:3)

18 Ar/CF4/isoC4H10 (76:20:4)

19 Ar/CF4/isoC4H10 (75:20:5)

20 Ar/CF4/isoC4H10 (74:20:6)

21 Ar/CF4/isoC4H10 (73:20:7)

22 Ar/CF4/isoC4H10 (72:20:8)

23 Ar/CF4/isoC4H10 (73:25:2)

24 Ar/CF4/isoC4H10 (72:25:3)

25 Ar/CF4/isoC4H10 (71:25:4)

26 Ar/CF4/isoC4H10 (70:25:5)

27 Ar/CF4/isoC4H10 (69:25:6)

28 Ar/CF4/isoC4H10 (67:30:3)

29 Ar/CF4/isoC4H10 (66:30:4)

30 Ar/CF4/isoC4H10 (65:30:5)

CF4 base

Ar/C2H6 (90:10) base

Fixing CF4 ratiochanging Ar and isoC4H10 ratio

-PIC : 2-D gaseous detector

10cm

Size: 10 cm x 10 cmPixel pitch: 400 m ~ 65,000 pixelsGas gain: ~6,000 (stable operation of more than 1 month)

400μm pitch

anode cathode

Cu

-PIC : gain and Energy spectrum

Gas gain uniformityRMS ~ 7%

Energy spectrum (55Fe)

E/E 30% @ 5.9 keV

Ar-escape

0 2 4 6 8 10Energy [keV]

We filled with Ar(90%) + C2H6(10%) gas at 1atm

X-ray imaging with -PIC

Test chart imageTest chart imagePosition resolution:120 m

AMP-Discri. BoardBased on a chip for ATLAS Thin Gap Chamber0.8V/pC

1 mm

Proton Therapy

150MeVproton

200MeV

Depth in Tissue (water) [mm]

Attack on Cancerous cells

proton

Gammarays

neutronWater phantom

Simulation studyETCC :ability to detect Prompt gamma rays as the monitor

Wide energy range (0.1-10 MeV)Rejection of Neutron Wide field of view (~3 str.)

511keV2.2MeV

Gamma raysneutron

Simulation

Monitoring Before treatment:

ionization chamber After treatment:

PET technique　　 (PET: positron emission tomography)

Real time : none

We are developing a monitor for Proton Therapy

160 MeV Proton

Water Phantom

ETCC(10cm)3 TPC

30cm

Experiment in Osaka Univ. Research Center for Nuclear Physics (RCNP)

collaborator :J. Kim(Research Institute and Hospital, National Cancer Center, Korea)

Sensitivity in X / Gamma-ray Astronomy

bad

good

1mCrabEGRET

AirCherenkovFermi

～１ °

suzakuHXD

co

nti

nu

ou

s s

ens

itiv

ity

[e

rg/c

m2/s

ec

]energy [eV]

Our goal

keV GeV TeVMeV

Energy spectrumdiffuse cosmic rays atmospheric rays

SMILE-1

Previous results

10 102 103 104 105

[Energy]

Flu

x [p

hot

ons

/ (c

m2 s

ec

str

keV

)]

10-1

10-3

10-5

10-7

SMILE-1

Previous results

Flu

x [p

hot

ons

/ (c

m2 s

ec

str

keV

(g

/ cm

2))

]

10-2

10-4

10-6

10-8

10 102 103 104 105

[Energy]

We detected 420 photons (Total)@0.15-1 MeV, 32-35 km for 4 hours