Development of nuclear emulsion detectors for cosmic-ray muon radiography and its applications
Cosmic-ray muon radiography is a nondestructive inspection technique of large structures. The principle is the measurement of absorption rate of cosmic-ray muon, which comes from all directions, inside the target material. Thus, This technique needs to measure three-dimensional incoming angles of each muons and compare the detected number of muons with the expected number of muons.
Nuclear emulsion is high-sensitive photographic film for detecting three-dimensional trajectories of charged particles with very high position resolution (sub micrometers), which gives us very high angular resolution (a few milliradians). Thanks to these properties, the detector size is compact (thickness is less than 1millimeter per plate), the weight is light, and no need of electric power supply. And also, it’s easy to prepare multiple detectors placed around the target for the tomography. These features are advantages for muon radiography experiment in outdoor (example: volcanoes, archeological monuments) or disaster site (example: Fukushima Daiichi Nuclear Power Plant) observation.
We are developing the nuclear emulsion by ourselves by using gel production machine and its pouring techniques for mass production at Nagoya University. Latest nuclear emulsions produced in our laboratory are already used for the muon radiography experiment.
In this talk, I’ll present overview of cosmic-ray muon radiography and the status of development of nuclear emulsion detector. In addition, on-going experiment and future prospect will be also presented.