Abstract
Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion) experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.
Highlights
The observation of high-energy cosmic gamma rays provides the origins and acceleration mechanism of highenergy cosmic rays in the universe
To detect gamma rays in nuclear emulsion detectors, the leading point of the electron-positron pair created by a gamma-ray has been measured with precise submilliradian angular resolution in emulsion films; the gamma ray arrival direction and momentum can be precisely determined
The nuclear emulsion films had been exposed to cosmic radiation at this height directly, and we expected comic ray nuclei components including He nuclei and heavier ones
Summary
The observation of high-energy cosmic gamma rays provides the origins and acceleration mechanism of highenergy cosmic rays in the universe. Fermi-LAT [1, 2] reported observations of more than three thousand gamma ray point sources including 30 percent unidentified objects. To explore these sources in detail, a more precise angular resolution has been needed in the gamma ray energy range of 10 MeV–100 GeV. The nuclear emulsion films had been exposed to cosmic radiation at this height directly, and we expected comic ray nuclei components including He nuclei and heavier ones. In the GRAINE balloon flight [3], the detection of these cosmic ray nuclei components was examined with image analysis technologies as well as time-stamper systems
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