1. Development of an Electron-Tracking Compton Camera using CF 4 gas at high pressure for improved detection efficiency Michiaki Takahashi N. Higashi, S. Iwaki, S. Kabuki, H. Kubo, S. Kurosawa, K. Miuchi, K. Nakamura, J. D. Parker, T. Sawano, A. Takada A, T. Tanimori, K. Taniue, and K. Ueno Dept. of Physics, Graduate school of Science, Kyoto University, Kyoto, Japan A ISAS/JAXA, Kanagawa, Japan The Twelfth Vienna Conference on Instrumentation, Vienna, Austria 20 February 2010

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

3. 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 μPIC GEM e-e- B26 K. Ueno, A22 S. Kurosawa 2 events １ 23 5 10100  Determination of direction and energy of each incident gamma ray  Large FOV (  3 sr)

4. 10 cm 400  m pitch anode cathode Proton 10cm Electron Example of 3D track Electric field  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 cm 3 Gas : Ar/C 2 H 6 (90:10) at 1 atm, sealed Position resolution :  150  m (1D) Stable gas gain :  30000 (  PIC :  3000, GEM :  10)

5. GSO and LaBr 3 Scintillation Cameras GSO 8×8 Pixel 13 mm 6 mm 15 x 15 cm 2 Camera (GSO or LaBr 3 + Multi anode PMT (H8500, HPK)) Number of pixels: 576 Pixel size 6×6×13 mm 3 (GSO) 6×6×15 or 20 mm 3 (LaBr 3 ) GSO Energy resolution :10.0 % (@662keV, FWHM) LaBr 3 Energy resolution: 6.5% (@662keV, FWHM) Position resolution: 6mm Black :GSO Red : LaBr3 15 cm 5 cm

6. 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 : LaBr 3 Scinti : GSO

7. Energy window : ±10% 1004  1228 keV Examples of Medical Imaging Zn-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 : LaBr 3 2 sources imaging ETCC for medical use Activity : 0.16 MBq Time : 110.5 hours Events : 173 events Scintillator  TPC Time : 6 hours ETCC/CT Spatial resolution  10 mm (FWHM)

8. Improvement of detection efficiency Optimization of gas Operation at high pressure Increase detection area Multi-head camera (10×10×10 cm 3 ×2,3,…) Developing a large size ETCC (30×30×30 cm 3 ) For High Sensitivity 2 times better than our prototypes

9. Demerit of CF 4 gas Low gas gain  isoC 4 H 10 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/C 2 H 6 (90:10)  CF 4 gas mixture

10. Drift Cage 10 cm Optimize the gas mixture Electronics  TPC source GEM (SciEnergy)  PIC Gas Ar/C 2 H 6 (90:10) Ar CF 4 isoC 4 H 10 Measurement 1.Gas Gain 2.Position Resolution Requirements : High CF 4 ratio Gas Gain  20,000 10 cm

11. CF 4 45% CF 4 50% Improved by more than 2 by introducing isoC 4 H 10 This gas  GEM = 340V The other  GEM = 400V CF 4 20% CF 4 30% CF 4 40% Gas Gain at 1 atm  Penning effect of isoC 4 H 10 

12.  = 162  m D = 81  m/cm 1/2 Ar/CF 4 /isoC 4 H 10 (54:40:6) muon tracks  = 156  m D = 175  m/cm 1/2 Better by factor 2 l : Drift length D : Diffusion Constant Position Resolution Ar/C 2 H 6 (90:10)

13. Ar/C 2 H 6 (90:10) at 1 atm Ar/C 2 H 6 (90:10) at 2 atm Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1 atm Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1.4 atm Measurement 1.Gas Gain 2.Drift Velocity 3.Position Resolution 4.Energy Resolution High Pressure 100 mm 2 mm 100  mt GEM 2 mm 100 mm 50  mt GEM  PIC Drift Plane (Al Mylar) Electronics  TPC source

14. Gas Gain Upper  GEM = 350V Lower  GEM = 250V Upper  GEM = 460V Lower  GEM = 360V Upper  GEM = 500V Lower  GEM = 380V Upper  GEM = 610V Lower  GEM = 450V Lower gas gain

15. Drift Velocity Difference between simulation and measurement is smaller than  10%

16. Position Resolution Ar/C 2 H 6 (90:10) at 1 atm Ar/C 2 H 6 (90:10) at 2 atm Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1 atm Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1.4 atm  = 332  m, D = 246  m/cm 1/2  = 302  m, D = 204  m/cm 1/2  = 378  m, D = 147  m/cm 1/2  = 330  m, D = 128  m/cm 1/2 Better by factor  2 Better by factor  1.6

17. Energy Resolution 31 keV X-ray from 133 Ba (31 keV) Ar/C 2 H 6 (90:10) at 1 atmAr/C 2 H 6 (90:10) at 2 atm Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1 atm Ar/CF 4 /isoC 4 H 10 (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

18. Imaging with ETCC gamma-ray from 133 Ba (356 keV, 800 kBq) Electronics  TPC source GSO Scintillation Camera Measurement 1.Efficiency 2.Angular resolution (ARM and SPD) 15 cm ARM : Angular Resolution Measure SPD : Scatter Plane Deviation

19. Efficiency and Angular Resolution ( 133 Ba 356 keV) GasPressureEfficiencyARM (FWHM)SPD (FWHM) Ar/C 2 H 6 (90:10)1 atm 1.81×10 -5 10.4°114.8° Ar/C 2 H 6 (90:10)2 atm 3.55×10 -5 11.1°105.1° Ar/CF 4 /isoC 4 H 10 (54:40:6)1 atm 2.44×10 -5 11.7°117.9° Ar/CF 4 /isoC 4 H 10 (54:40:6)1.4 atm 3.51×10 -5 11.2°119.1° ARM (FWHM) [degree] 10 1 50 5 SMILE-I 2006 (Xe + GSO) Ar/C 2 H 6 TPC + GSO scintillator the highest spec. This Work (GSO) Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1.4 atm Imaging of 133 Ba 15 cm away from top of  TPC better by factor 1.94 Ar/C 2 H 6 TPC + LaBr 3 scintillator

20. 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 CF 4 gas with steady gas gain of  20,000 is Ar/CF 4 /isoC 4 H 10 (54:40:6). The diffusion constant of Ar/CF 4 /isoC 4 H 10 (54:40:6) is 2 times better than that of Ar/C 2 H 6 (90:10), so the position resolution is improved. The efficiency for the ETCC using Ar/CF 4 /isoC 4 H 10 (54:40:6) at 1.4 atm is 2 times higher than that using Ar/C 2 H 6 (90:10) at 1 atm, and those ARMs are comparable (  11  at 356 keV (FWHM)).

21. Thank you for your attention

22. Vs. Conventional Compton Camera Advanced Conventional Reconstruction : circle Direction error region : donut DO NOT measure the track of a Recoil electron 150 events 600 events -15 15 X [cm] Y [cm] -15 15X [cm] 15 Y [cm] 137 Cs(1MBq)  2, Classical Compton 137 Cs(1MBq)  2, Advanced Compton Measure the 3-D track of a Recoil electron Reconstruction : point Direction error region: arc COMPTEL Our ETCC

23. Position-Sensitive Scintillation Camera 13mm 6 mm 5cm Multi-anode Photo Multiplier Tube (PMT) HPK H8500 8x8 anodes GSO(Ce) 8x8 pixels Pixel size: 6x6x13mm 3 5cm -0.8 -0.4 0 0.4 0.8 X-position (a. u.) 0.8 0.4 0 -0.4 -0.8 Y-position (a. u) 500 400 300 200 100 0 Counts (a. u.) 2-D image in flood-field irradiation 137 Cs Dynamic energy range: 0.08 -1 MeV Eng. Resolution: 10.5 % @662 keV

24. Assembly of LaBr 3 (Ce) array 6.1 mm pitch Using our technique, we assembled an 8  8 array. 54mm 20mm (=multi-anode PMT H8500 anode pitch) GSO array LaBr 3 array LaBr 3 FWHM(%)= (5.7  0.4)  (E/662keV) - 0.53  0.01 GSO FWHM(%)= (10.4  0.3)  (E/662keV) -0.51  0.01 LaBr 3 ： hygroscopic Hermetic package GSO monolithic LaBr 3 monolithic 133 Ba  E/E = 4.1  0.1 % @ 356 keV (FWHM)

25. Angular Res. Simulation including  TPC Scattered  E : energy Recoil e - K: energy Scattering angle φ  Incident   φ Angular resolution (ARM) Calculated assuming 1, no error in position of Compton point 2, energy Res. of TPC : 30 % @ 22 keV Eng. Res. (FWHM) of LaBr 3 (Ce) : ~ 3 % @ 662 keV Loef et al. (2001) Doppler broadening (Ar) Zoglauer et al. (2003) Angular resolution (FWHM) [degree] 10.5 % 4.2  7% 3.1  5% 2.3  3% 2.1  Sci. Eng. Res. @662keV ETCC. Angular Res. @662keV(FWHM)

26. 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 Ener gy [keV] 167320354364412511, 1275 511 6628351095, 1292 11161173, 1333 Energy dynamic range : 167 – 1333 keV. Measured sources SPECTPET 26

27. Spatial resolution vs. Energy Goal : Same resolution as human PET @ 511keV Spatial Resolution 27

28. I-131-MIBG & F-18-FDG imaging (365 & 511 keV) PET/SPECT/CT Rainbow ： PET Orange ： SPECT Rainbow ： 511keV Orange ： 365keV PC12 Brown fat cell PC12 Brown fat cell 6cm Dept. of Bioanalysis, Kyoto University H. Kimura, H. Amano and H. Saji Scinti : LaBr 3

29. Zn-65 mouse imaging Measurement after dissection Liver :0.04 MBq Spleen :0.02 Pancreas:0.02 Heart :0.02 Stomach : 0.01 Kidney : 0.00 Intestinal:0.11 Brain :0.02 Other :0.79 BG :0.03 Mouse Zn-65 imaging Energy : 1116keV activity : 1.4MBq obs. time : 2784 min Events : 629 events 3x3 LaBr 3 Install to 10cm-ETCC Zn is a good tracer for diabetes

30. All kinds of experiment gas (45 types) No. Gas 1CF 4 /isoC 4 H 10 (95:5) 2CF 4 /isoC 4 H 10 (90:10) 3CF 4 /isoC 4 H 10 (80:20) 4Ar/C 2 H 6 (90:10) 5Ar/C 2 H 6 /CF 4 (72:8:10) 6Ar/C 2 H 6 /CF 4 /isoC 4 H 10 (69.3:7.7:20:3) 7Ar/C 2 H 6 /CF 4 (63:7:30) 8Ar/C 2 H 6 /CF 4 (54:6:40) 9Ar/C 2 H 6 /CF 4 (45:5:50) 10Ar/C 2 H 6 /CF 4 /isoC 4 H 10 (42.3:4.7:50:3) 11Ar/C 2 H 6 /CF 4 (27:3:70) 12Ar/CF 4 /isoC 4 H 10 (95:3:2) 13Ar/isoC 4 H 10 (90:10) 14Ar/CF 4 (90:10) 15Ar/CF 4 (80:20) No. Gas 31Ar/CF 4 /isoC 4 H 10 (64:30:6) 32Ar/CF 4 /isoC 4 H 10 (63:30:7) 33Ar/CF 4 /isoC 4 H 10 (56:40:4) 34Ar/CF 4 /isoC 4 H 10 (55:40:5) 35Ar/CF 4 /isoC 4 H 10 (54:40:6) 36Ar/CF 4 /isoC 4 H 10 (53:40:7) 37Ar/CF 4 /isoC 4 H 10 (52:40:8) 38Ar/CF 4 /isoC 4 H 10 (49:45:6) 39Ar/CF 4 /isoC 4 H 10 (47:50:3) 40Ar/CF 4 /isoC 4 H 10 (46:50:4) 41Ar/CF 4 /isoC 4 H 10 (45:50:5) 42Ar/CF 4 /isoC 4 H 10 (44:50:6) 43Ar/CF 4 /isoC 4 H 10 (43:50:7) 44Ar/CF 4 /isoC 4 H 10 (42:50:8) 45Ar/CF 4 /isoC 4 H 10 (40:50:10) No. Gas 16Ar/CF 4 /isoC 4 H 10 (78:20:2) 17Ar/CF 4 /isoC 4 H 10 (77:20:3) 18Ar/CF 4 /isoC 4 H 10 (76:20:4) 19Ar/CF 4 /isoC 4 H 10 (75:20:5) 20Ar/CF 4 /isoC 4 H 10 (74:20:6) 21Ar/CF 4 /isoC 4 H 10 (73:20:7) 22Ar/CF 4 /isoC 4 H 10 (72:20:8) 23Ar/CF 4 /isoC 4 H 10 (73:25:2) 24Ar/CF 4 /isoC 4 H 10 (72:25:3) 25Ar/CF 4 /isoC 4 H 10 (71:25:4) 26Ar/CF 4 /isoC 4 H 10 (70:25:5) 27Ar/CF 4 /isoC 4 H 10 (69:25:6) 28Ar/CF 4 /isoC 4 H 10 (67:30:3) 29Ar/CF 4 /isoC 4 H 10 (66:30:4) 30Ar/CF 4 /isoC 4 H 10 (65:30:5) CF 4 base Ar/C 2 H 6 (90:10) base Fixing CF 4 ratio changing Ar and isoC 4 H 10 ratio

31.  -PIC : 2-D gaseous detector 10cm Size: 10 cm x 10 cm Pixel pitch: 400  m ~ 65,000 pixels Gas gain:  ~6,000 (stable operation of more than 1 month) 400μm pitch anode cathode Cu

32.  -PIC : gain and Energy spectrum Gas gain uniformity RMS ~ 7% Energy spectrum ( 55 Fe)  E/E 30% @ 5.9 keV Ar-escape 0 2 4 6 8 10 Energy [keV] We filled with Ar(90%) + C 2 H 6 (10%) gas at 1atm

33. X-ray imaging with  -PIC Test chart image Position resolution: 120  m AMP-Discri. Board Based on a chip for ATLAS Thin Gap Chamber 0.8V/pC 1 mm

34. Proton Therapy 150MeV proton 200MeV Depth in Tissue (water) [mm] Attack on Cancerous cells proton Gamma rays neutron Water phantom Simulation study ETCC :  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.) 511keV 2.2MeV Gamma rays neutron Simulation Monitoring Before treatment: ionization chamber After treatment: PET technique (PET: positron emission tomography) Real time : none

35. 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)

36. Sensitivity in X / Gamma-ray Astronomy ba d good 1mCrab EGRET Air Cherenkov Fermi ～１ ° suzaku HXD continuous sensitivity [erg/cm 2 /sec] energy [eV] Our goal keVGeVTeVMeV

37. Energy spectrum diffuse cosmic  rays atmospheric  rays SMILE-1 Previous results 10 10 2 10 3 10 4 10 5 [Energy] Flux [photons / (cm 2 sec str keV)] 10 -1 10 -3 10 -5 10 -7 SMILE-1 Previous results Flux [photons / (cm 2 sec str keV (g / cm 2 ))] 10 -2 10 -4 10 -6 10 -8 10 10 2 10 3 10 4 10 5 [Energy] We detected 420 photons (Total) @0.15-1 MeV, 32-35 km for 4 hours