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

Journal Article · Tue Sep 01 00:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/810/1/28· OSTI ID:22525511

Tanimori, T.; Kubo, H.; Takada, A.; Iwaki, S.; Komura, S.; Matsuoka, Y.; Miyamoto, S.; Mizumoto, T.; Mizumura, Y.; Nakamura, K.; Nakamura, S.; Oda, M.; Parker, J. D.; Sawano, T.; Sonoda, S.; Takemura, T.; Tomono, D.; Ueno, K. ^[1]; Kurosawa, S. ^[2]

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1. Department of Physics, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan)
2. Institute of Materials Research, Tohoku University, 980-8577 Sendai (Japan)

Photon imaging for MeV gammas has serious difficulties due to huge backgrounds and unclearness in images, which originate 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 a mere ∼30 persistent sources. It is in stark contrast with the ∼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 helpful to reduce the background under conditions similar to those in 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{sup −12} erg cm{sup −2} s{sup −1} at 1 MeV.

• OSTI ID: 22525511
• Journal Information: Astrophysical Journal, Vol. 810, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPTON EFFECT
COSMIC GAMMA BURSTS
ELECTRONS
ENERGY LOSSES
GAMMA ASTRONOMY
GAMMA DETECTION
GAMMA RADIATION
GEV RANGE
MEV RANGE
MULTIPLE SCATTERING
NUCLEOSYNTHESIS
PHOTONS
SENSITIVITY
SPACE
SPECTROSCOPY
SUPERNOVAE
TELESCOPES
UNIVERSE