In order to explore MeV gamma-ray astronomy, we have developed the Electron Tracking Compton Camera (ETCC)
consisting of a Time projection Chamber based on the micro pixel gas counter and pixel array scintillators. By measuring the track of a recoil electron in the TPC event by event, the ETCC measures the direction of each gamma-ray, and provides both good background rejection and an angular resolution over ~1 degree. A 1m-cubic size ETCC in satellite would be a good candidate for an All sky MeV gamma-ray survey of a wide band energy region of 0.1-100MeV with several ten times better sensitivity than COMPTEL. Already we carried out a balloon experiment with a small ETCC
(Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-I) in 2006, and measured diffuse cosmic and
atmosphere gamma rays. We are now constructing a 30cm-cube ETCC to catch gamma-rays from the Crab and
terrestrial gamma-ray bursts at the North Pole from 2013 (SMILE-II project). Terrestrial gamma-ray bursts are generated
by relativistic electron precipitation in the Pole region. Recently performance of tracking a recoil electron has been
dramatically improved, which may enable us to reach the ideal efficiency expected for the detector. In addition, we
mention about the unique capability to find a high-z Gamma-Ray Bursts beyond z>10 by ETCC, in particular long
duration GRBs over 1000 sec, which are expected to be due to POP-III stars.
We have developed a sub-MeV and MeV gamma-ray imaging Compton camera for use in gamma-ray astronomy; it
consists of a gaseous time-projection chamber (TPC) to convert the Compton scattering events and a scintillator array to
absorb photons. The TPC measures the energy and three-dimensional tracks of Compton-recoil electrons, while the pixel
scintillator arrays measure the energy and positions of scattered gamma rays. Therefore, our camera can reconstruct the
incident gamma rays, event by event, over a wide field of view of approximately 3 str. We are now developing a
Compton camera for a balloon-borne experiment.
We have developed an Electron-Tracking Compton Camera (ETCC) based on a gaseous micro Time Projection Chamber (ETCC) based on a gaseous micro Time Projection Chamber (μ-TPC) which measures the direction and the energy of the recoil electron and a GSO(Ce) scintillation camera which surrounds the μ-TPC
and measures the Compton scattered gamma ray. If not measuring a direction of a recoil electron, a direction of the
incident gamma-ray could only be reconstructed as a circle. Measuring the direction of the recoil electron reduces the Compton cone
to a point, and thus reconstructs the incident direction completely for a single photon and realizes the strong background
rejection. Using the ETCC with a detection volume of about 10cm×10cm×15cm, we had the balloon-borne experiment
supported by ISAS/JAXA in 2006 for the purpose of the observation of diffuse cosmic and atmospheric gamma rays. The ETCC
obtained about 200 photons with FOV of 3 str in 3 hours in the energy range from 100 keV to 1 MeV, and the obtained flux was
consistent with previous observations. On the basis of the results, we are developing the large size ETCC in order to improve the effective area for the next balloon
experiment. The large size ETCC has the detection volume of 23cm ×28cm×30cm which consists of the
23cm×28cm×30cm μ-TPC and the 30cm×30cm×1.3cm scintillation camera. Then we
obtained the gamma-ray image and investigated the first performances of the large size ETCC. The Angular Resolution Measure
(ARM) and the Scatter Plane Deviation (SPD) are 12.1 degree and 117 degree (FWHM) at 662keV, respectively, and the energy
resolution is 16.9%(FWHM) at 662keV.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.