SMILE-II: Balloon-Borne Telescope for Background-Suppressed Soft Gamma-Ray Imaging

Sawano, Tatsuya; Tanimori, T.; Kubo, H.; Takada, Atsushi; Parker, Joseph D.; Mizumoto, Tetsuya; Sonoda, S.; Tomono, D.; Nakamura, K.; Matsuoka, Yoshihiro; Komura, Shingo; Sato, Yuki; Nakamura, Shōgo; Miuchi, K.; Kabuki, S.; Kishimoto, Y.; Kurosawa, Shunsuke; Iwaki, S.; Tanaka, Mikito; Ikeno, M.; Uchida, T.

doi:10.7566/jpscp.1.013099

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…This good performance is about one order higher than the previous SMILE-I type ETCC. Furthermore, our obtained efficiencies for a few hundred keV band are consistent within 10% with the simulation which takes into account only physical processes [9]. It means almost all of the fully-contained Compton recoil electrons are detected by the TPC.…”

Section: Results Of Performance Testsupporting

confidence: 83%

Development of a 30 cm-cube Electron-Tracking Compton Camera for the SMILE-II Experiment

Mizumura¹,

Tanimori²,

Kubo³

et al. 2014

J. Inst.

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To explore the sub-MeV/MeV gamma-ray window for astronomy, we have developed the Electron-Tracking Compton Camera (ETCC), and carried out the first performance test in laboratory conditions using several gamma-ray sources in the sub-MeV energy band. Using a simple track analysis for a quick first test of the performance, the gamma-ray imaging capability was demonstrated with clear images and 5.3 degrees of angular resolution measure (ARM) measured at 662 keV. As the greatest impact of this work, a gamma-ray detection efficiency on the order of 10 −4 was achieved at the sub-MeV gamma-ray band, which is one order of magnitude higher than our previous experiment. This angular resolution and detection efficiency enables us to detect the Crab Nebula at the 5σ level with several hours observation at balloon altitude in middle latitude. Furthermore, good consistency of efficiencies between this performance test and simulation including only physical processes is very important; it means we achieve nearly 100% detection of Compton recoil electrons and means that our predictions of performance enhancement resulting from future upgrades are more realistic. We are planning to confirm the imaging capability of the ETCC by observation of celestial objects in the SMILE-II (Sub-MeV gamma ray Imaging Loadedon-balloon Experiment II). The SMILE-II and following SMILE-III project will be an important key of sub-MeV/MeV gamma-ray astronomy.

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Section: Results Of Performance Testsupporting

confidence: 83%

Development of a 30 cm-cube Electron-Tracking Compton Camera for the SMILE-II Experiment

Mizumura¹,

Tanimori²,

Kubo³

et al. 2014

J. Inst.

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“…For the calculation of the red lines, we used Geant4 [14] and only considered the 1.5 atm Ar-C 2 H 6 gas mixture in the drift region of the TPC and GSO scintillator arrays and do not consider other structure such as the vessel. For the calculation of the efficiency from the simulated result, we followed the event detection criteria written in reference [13]. As shown in the figure, the detection efficiency for 662 keV gamma rays from the center of the FoV is (9.31 ± 0.95) × 10 − 5 .…”

Section: Gamma-ray Detection Efficiencymentioning

confidence: 99%

“…(Left) Red points and line show the measured and simulated results of the energy dependence of the detection efficiency of the ETCC for gamma rays from the center of the FoV. The blue points and line are the measured and simulated results for a similar ETCC that used 1-atm gas for the TPC and GSO pixels of thickness 13 mm, respectively[8,13]. (Right) Red points and line show the measured and simulated data of the angular dependence of the 662 keV gamma-ray detection efficiency of the ETCC, respectively.…”

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A performance study of an electron-tracking Compton camera with a compact system for environmental gamma-ray observation

et al. 2015

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An electron-tracking Compton camera (ETCC) is a detector that can determine the arrival direction and energy of incident sub-MeV/MeV gamma-ray events on an event-by-event basis. It is a hybrid detector consisting of a gaseous time projection chamber (TPC), that is the Compton-scattering target and the tracker of recoil electrons, and a position-sensitive scintillation camera that absorbs of the scattered gamma rays, to measure gamma rays in the environment from contaminated soil. To measure of environmental gamma rays from soil contaminated with radioactive cesium (Cs), we developed a portable battery-powered ETCC system with a compact readout circuit and data-acquisition system for the SMILE-II experiment [1], [2]. We checked the gammaray imaging ability and ETCC performance in the laboratory by using several gamma-ray point sources. The performance test indicates that the field of view (FoV) of the detector is about 1 sr and that the detection efficiency and angular resolution for 662 keV gamma rays from the center of the FoV is (9.31 ± 0.95) × 10 − 5 and 5.9 • ± 0.6 • , respectively. Furthermore, the ETCC can detect 0.15 µSv/h from a 137 Cs gamma-ray source with a significance of 5σ in 13 min in the laboratory. In this paper, we report the specifications of the ETCC and the results of the performance tests. Furthermore, we discuss its potential use for environmental gamma-ray measurements.

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AN ELECTRON-TRACKING COMPTON TELESCOPE FOR A SURVEY OF THE DEEP UNIVERSE BY MeV GAMMA-RAYS

Tanimori

Kubo

Takada

et al. 2015

ApJ

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Photon imaging for MeV gammas has serious difficulties due to huge backgrounds and unclearness in images, which are originated from incompleteness in determining the physical parameters of Compton scattering in detection, e.g., lack of the directional information of the recoil electrons. The recent major mission/instrument in the MeV band, Compton Gamma Ray Observatory/COMPTEL, which was Compton Camera (CC), detected mere ∼ 30 persistent sources. It is in stark contrast with ∼2000 sources in the GeV band. Here we report the performance of an Electron-Tracking Compton Camera (ETCC), and prove that it has a good potential to break through this stagnation in MeV gamma-ray astronomy. The ETCC provides all the parameters of Compton-scattering by measuring 3D recoil electron tracks; then the Scatter Plane Deviation (SPD) lost in CCs is recovered. The energy loss rate (dE/dx), which CCs cannot measure, is also obtained, and is found to be indeed helpful to reduce the background under conditions similar to space. Accordingly the significance in gamma detection is improved severalfold. On the other hand, SPD is essential to determine the point-spread function (PSF) quantitatively. The SPD resolution is improved close to the theoretical limit for multiple scattering of recoil electrons. With such a well-determined PSF, we demonstrate for the first time that it is possible to provide reliable sensitivity in Compton imaging without utilizing an optimization algorithm. As such, this study highlights the fundamental weak-points of CCs. In contrast we demonstrate the possibility of ETCC reaching the sensitivity below 1×10 −12 erg cm −2 s −1 at 1 MeV.

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SMILE-II: Balloon-Borne Telescope for Background-Suppressed Soft Gamma-Ray Imaging

Cited by 4 publications

References 19 publications

Development of a 30 cm-cube Electron-Tracking Compton Camera for the SMILE-II Experiment

Development of a 30 cm-cube Electron-Tracking Compton Camera for the SMILE-II Experiment

A performance study of an electron-tracking Compton camera with a compact system for environmental gamma-ray observation

AN ELECTRON-TRACKING COMPTON TELESCOPE FOR A SURVEY OF THE DEEP UNIVERSE BY MeV GAMMA-RAYS

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