MeV gamma-ray observation with a well-defined point spread function based on electron tracking

A. Takada, T. Tanimori, H. Kubo, T. Mizumoto, Y. Mizumura, S. Komura, T. Kishimoto, T. Takemura, K. Yoshikawa, Y. Nakamasu, Y. Matsuoka, M. Oda, S. Miyamoto, S. Sonoda, D. Tomono, K. Miuchi, S. Kurosawa, T. Sawano

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


The field of MeV gamma-ray astronomy has not opened up until recently owing to imaging difficulties. Compton telescopes and coded-aperture imaging cameras are used as conventional MeV gamma-ray telescopes; however their observations are obstructed by huge background, leading to uncertainty of the point spread function (PSF). Conventional MeV gamma-ray telescopes imaging utilize optimizing algorithms such as the ML-EM method, making it difficult to define the correct PSF, which is the uncertainty of a gamma-ray image on the celestial sphere. Recently, we have defined and evaluated the PSF of an electron-tracking Compton camera (ETCC) and a conventional Compton telescope, and thereby obtained an important result: The PSF strongly depends on the precision of the recoil direction of electron (scatter plane deviation, SPD) and is not equal to the angular resolution measure (ARM). Now, we are constructing a 30 cm-cubic ETCC for a second balloon experiment, Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-II. The current ETCC has an effective area of ∼1 cm2 at 300 keV, a PSF of ∼10° at FWHM for 662 keV, and a large field of view of ∼3 sr. We will upgrade this ETCC to have an effective area of several cm2 and a PSF of ∼5° using a CF4-based gas. Using the upgraded ETCC, our observation plan for SMILE-II is to map of the electron-positron annihilation line and the 1.8 MeV line from 26Al. In this paper, we will report on the current performance of the ETCC and on our observation plan.

Original languageEnglish
Title of host publicationSpace Telescopes and Instrumentation 2016
Subtitle of host publicationUltraviolet to Gamma Ray
EditorsMarshall Bautz, Tadayuki Takahashi, Jan-Willem A. den Herder
ISBN (Electronic)9781510601895
Publication statusPublished - 2016
EventSpace Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray - Edinburgh, United Kingdom
Duration: 2016 Jun 262016 Jul 1

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSpace Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray
Country/TerritoryUnited Kingdom


  • balloon experiment
  • Compton telescope
  • MeV gamma-ray astronomy


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