Latest emulsion detector for cosmic ray observation: high sensitive emulsion film and high speed readout system

Hiroki Rokujo
2016 Proceedings of The 34th International Cosmic Ray Conference — PoS(ICRC2015)   unpublished
A nuclear emulsion is used in a high-resolution 3D tracking device. AgBr crystals of 0.2 µm size that are penetrated by a charged particle grow, via a chemical development process, into 0.8 µm silver grains that can be observed as a track by using a microscope. Recent fully automated readout systems have enabled not only high-resolution measurements but also large-scale experiments (accelerator and balloon-borne experiments, cosmic ray muon radiography, etc.). Since 2010, properties of the
more » ... ion detector have drastically changed. We have introduced a system of nuclear emulsion gel production to the laboratory in Nagoya University, Japan, and have started self-development and supply of the new gel, instead of relying on photographic film companies. We have also developed a next-generation readout system, the Hyper Track Selector (HTS). The scanning speed is designed to be 0.9 m 2 /h (100 times faster than the current system). Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE) is a cosmic gamma-ray observation project that uses a balloon-borne emulsion detector. The angular resolution of the emulsion gamma-ray telescope (0.08 • @ 1-2 GeV) is one order of magnitude higher than that of the Fermi-LAT. In addition, it has polarization sensitivity using the pair creation mode. A search for exotic particles and measurements of short-lived particle production rates in cosmic rays at balloon altitudes will be also conducted. In the second GRAINE balloon-borne experiment in 2015 May, 50 m 2 of the new highly sensitive emulsion films were used for the medium-scale gamma-ray telescope (aperture area 3600 cm 2 ), with which we demonstrate the imaging performance. We present the status of the latest emulsion detector and readout system based on results of performance tests conducted for the GRAINE balloon-borne experiment in 2015.
doi:10.22323/1.236.0654 fatcat:ce3p24ka6jhvlaqokwrd2fj66q