Development of nuclear emulsion for muography

Muography (cosmic-ray muon radiography) is the non-destructive inspection by using muons produced by interactions between primary cosmic-rays and the Earth's atmosphere. The principle of this technology is the measurement of absorption of incoming cosmic-ray muons, just like X-ray imaging technology. A nuclear emulsion is the high sensitive photographic film used for detection of three-dimensional trajectory of charged particles such as muons with the position resolution of sub-micron. A nuclear emulsion has following properties: high spatial resolution with thin detector structure, lightweight, flexibility of detector size and no requirement of electric power supply. These properties of a nuclear emulsion are suitable for a detector of muography. We are developing the nuclear emulsion at Nagoya University. In this paper, the current performances of the nuclear emulsion and the fully self-production techniques developed at Nagoya University are described.