Experiment of the 30 cm-cube ETCC under the Intense Radiations with Proton Beam

Transcription

1 Experiment of the 30 cm-cube ETCC under the Intense Radiations with Proton Beam Contents Y. Matsuoka T. Tanimori, H. Kubo, A. Takada, J. D. Parker, T. Mizumoto, Y. Mizumura, S. Sonoda, D. Tomono, S. Iwaki, T. Sawano, K. Nakamura, S. Komura, S. Nakamura, T. Kishimoto, M.Oda, T. Takemura, S. Miyamoto (Kyoto Univ.) Compton Camera for MeV gamma-ray & S. Kurosawa (Tohoku Univ.) ETCC (Electron-Tracking Compton Camera) and SMILE project Performances of 30 cm-cube ETCC Experiment under the intense radiations

2 MeV gamma-ray astronomy MeV region CGRO/COMPTEL 1-30 MeV > 1 GeV GeV region Fermi/LAT ~30 objects/10 years ~2000 objects/2 years V. Schönfelder+ (A&AS, 2000) Detection sensitivity P. L. Nolan+ (ApJS, 2012) In the MeV region Bad erg / (cm 2 sec) Unclearness of image Sensitivity 1mCrab Astro-H goal Fermi EGRET Obs. Time : 10 6 sec Air Cherenkov Wide sensitivity gap What is the main reason of these problems? Good

3 ~2 m Difficulty of MeV gamma-ray Principle of COMPTEL Incomplete Compton reconstruction Usual Compton Cameras can t measure direction of the recoil electron. Imaging by superposition of event circles New Imaging method is needed. Artifact signals Background of Artifact COMPTEL V. Schönfelder+ (ApJS, 1993) Artifact Counts BG rejection by TOF (time of flight) Huge Background in space R. van Dijk (Ph.D thesis, 1996) produced by cosmic-ray interactions with detector BG rejection in COMPTEL was not sufficient. ~ 1/10 of the expected sensitivity TOF G. Weidenspointner+ (A&A, 2001) Powerful BG rejection is most important.

4 Electron-Tracking Compton Camera (ETCC) Gaseous- TPC Gaseous TPC : Tracker track and energy of a recoil electron Scintillator : Absorber position and energy of a scattered gamma-ray GSO Scintillators escaped e - from TPC de/dx distribution cosmic µ Fully contained e - Complete Reconstruction event by event 1 photon direction + energy Particle identification with de/dx Imaging method with direction of the electron

5 Comparison with the usual Compton method Electron-Tracking Compton Using the electron tracks complete direction within sector form error region Simply overlay High S/N No Artifacts Images of 137 Cs 2 m Usual Compton Imaging Not using the electron tracks only event circle within ring form error region Simply overlay Low S/N Artifacts appear 0.74 MBq 0.85 MBq 0.74 MBq 0.85 MBq Artifact 3.2 MBq 15 o 30 o 45 o 60 o Preliminary 662 kev ± 10% 3.2 MBq 15 o 30 o Electron tracks provide 4 times better S/N than usual Compton imaging! 45 o 60 o Preliminary

6 Balloon Experiment with ETCC (SMILE) Japan (2006) 10 x 10 x 15 cm 3 ETCC Small ETCC ~1 m old DAQ 10cm Ex: Electron track A. Takada+ (ApJ,2011) new DAQ ~4 cm stopped scattered Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment SMILE-II FM Measure diffuse cosmic & atmospheric gamma-ray km, 3 hours Measured : 420 events Simulation : ~400 events Succeed!! SMILE-II (Next) Gamma-ray Imaging test Observation of Crab > 5 σ Fort Sumner (middle 40 km, several hours TPC ~1 m Requirements SMILE-I Effective 300 kev > 0.5 cm cm 2 Angular 662 kev < Improvements Increasing the size of ETCC - 10 x 10 x 15 cm 3 (30 cm) 3 DAQ optimizing for ETCC - Tracking eff. : ~10% ~100% Scinti.

7 Performance (Effective area, Angular res.) Effective area Points: measured ( 139 Ce, 133 Ba, 22 Na, 137 Cs, 54 Mn; 1 2 m) SMILE-III 30cm-cubic (new DAQ, Xe 3 atm, 3 radiation length scintillator) SMILE-II (Now) Lines: simulated (not including detector response) Angular resolution 30cm-cubic (new DAQ, Ar 1 atm) 7.5 cm-cubic (new DAQ, Ar 1 atm) measured 5.3 o 662 kev SMILE-I type 10 cm-cubic (old DAQ, Ar 1 atm) SMILE-II ~1 cm 300 kev Experiment Simulation => ETCC obtains ~100 % of Compton events. We will upgrade to SMILE-III ~10 cm 2 [kev] Limit calculated from Energy & Position res. Satisfied the requirements for Crab detection.

8 Experiment with proton Simulation of 35 km Research Center for Nuclear Physics, Osaka Univ. gamma Neutrons are detected similar to Compton-γ neutron ETCC e + e - p DAQ Rate SMILE-II (expected) Hz Proton beam H2O Target Ratio of n/gamma (Liquid Scinti.) neutron Hz Extra detectors for env. monitor Liquid Scintillator 140MeV (neutron monitor) Proton na GSO Scintillator (gamma-ray spectrometer) kev Plastic Scintillator (particle counter) water target n/γ ~ Similar to background at balloon altitude Intensity ~ 5 x balloon altitude

9 Confirmation of background rejection power Imaging of 137 Cs(662 kev) φ20cm p (140 MeV) water Shield plate 137 Cs (0.8 MBq) MI escaped e proton Compto Preliminary n + p Raw data BG rejection (de/dx) gamma n, γ, p, Plastic Scintillator 30cm ETCC DAQ rate ~ 400 Hz 100cm 30cm use Electron track Fully contained e 137 Cs Lead shield beam line Preliminary 7.9σ 2.0σ Water target 15 o 30 o 45 o 60 o 662 kev beam line 15 o 30 o 45 o 60 o With de/dx selection, BG events are rejected. no use Electron track 137 Cs Lead shield Water target

10 DAQ (Data acquisition) rate Dead Time [%] Level Flight km DAQ Rate SMILE-I (32-35 km) Hz SMILE-II (expected) Hz Hz red : SMILE-I blue DAQ Rate [Hz] Data Trans. Limit < 1000 Hz DAQ Improvements Speed up the Data transfer rate - DAQ CPU upgrade x 2 Reduction of the Data - Selection and compression x 2-3 Dead-Time can be reduced to < 20 ~ 400 Hz

11 Detection sensitivity SMILE-I ΔE = E T obs = 10 6 s 3σ detection SMILE-II COMPTEL Crab nebula OSSE Preliminary SMILE-III EGRET IBIS SPI SMILE-satellite 1 mcrab Fermi SMILE-II : detectable Crab nebula with several hours at 40 km SMILE-III : Xe, 3 atm and 2-3 Radiation length GSO -> 10 times better sensitivity Satellite : (50 cm-cube, Xe 3 atm, 10 Rad. Len. LaBr 3 ) 4 -> reach to 1 mcrab

12 Summary ETCC has High contrast imaging Powerful background rejection with electron-track and de/dx selection SMILE-II ETCC has Effective Area ~ 1 cm 300 kev Angular Resolution 662 kev satisfied the requirements for Crab detection (Fort middle latitude, several hours at 40 km) Experiment with Proton Beam Intense radiations are available (5 times than balloon altitude) ETCC can clearly separate Compton-electron from neutrons ETCC maintains its sensitivity in high background Thank you for your attention!