Speaker
Description
We are advancing precise observations of cosmic gamma rays in the sub-GeV/GeV energy range using a large-scale nuclear emulsion telescope with high angular resolution (0.1° at 1 GeV), deployed on a balloon. We conducted balloon experiments in 2011, 2015, 2018, and 2023. In 2018, we achieved the first detection of an astronomical gamma-ray source and imaged the Vela pulsar with the worldʼs highest angular resolution in the sub-GeV region. In April 2023, we successfully conducted a 27-hour balloon flight during which the Vela pulsar and the region around the Galactic center were observed (GRAINE 2023).
The nuclear emulsion telescope consists of a converter, a time stamper, and an attitude monitor. The converter section is a stacked structure with nuclear emulsion films, capturing electrons and positrons from gamma rays. The high angular resolution of nuclear emulsion films enables precise determination of gamma-ray directions and momentum measurement through multiple Coulomb scattering.
We are developing new techniques for the detection of high-energy (>GeV) gamma rays. In the nuclear emulsion telescope, detection of high-energy gamma rays is challenging because the two tracks produced by pair production have an opening angle too narrow to be separated. Furthermore, the small scattering of the produced electrons and positrons makes it difficult to reconstruct the gamma-ray energy from momentum measurements. We introduce a new method to improve gamma-ray detection and momentum measurement for the nuclear emulsion telescope.
This presentation will report the current analysis of the GRAINE 2023 converter section and the new gamma-ray selection method under development.
| Collaboration(s) | GRAINE |
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