OPERA experiment aimed to observe νμ→ντ appearance, which have been indicated from muon neutrino deficit by Super Kamiokande. After 730 km of neutrino flight, tau neutrino should be appeared in muon neutrino beams. Tau lepton will emit when tau neutrino charge current interaction occurred. The existing of tau lepton at interaction vertex is the proof of tau neutrino. While the tau lepton’s track length is short as about 1 mm due to short life time hence fine position resolution such nuclear emulsion was needed.
Neutrinos interact with material with very rarely. This feature leads neutrino experiment to be huge target mass. OPERA used 9.3 million nuclear emulsion films, OPERA films cross section of 12.5 cm×10 cm, which had been produced by Fuji-Film. New technique to reduce the accumulated background tracks was developed. In order to accumulate neutrino events as much as possible, long period such as 5 years of neutrino exposure had been done. Finally OPERA established the tau neutrinos appearance through neutrino oscillation from muon neutrinos with this ideal device, nuclear emulsion.

We proposed the fine-grained nuclear emulsion as the new detector for direct detection of the dark matter which is one of the biggest challenges in the nature science. Stable micronization of silver halide crystal with 40 and 20 nm was succeed by construction of self-production system, and the detector capable of detection for submicron or shorter length tracks was realized for the first in the world. In addition, various technologies for super-high resolution analysis and high background rejection centering on the device have been developed, and the project for the directional dark matter search is promoted as international collaboration.

We are furthering GRAINE (Gamma-Ray Astro Imager with Nucler Emulsion) project which is the project of cosmic gamma-ray observation with balloon borne nuclear emulsion gamma-ray telescope. We describe the overview and the status of our project, as well as our future plan.

The nuclear emulsion technique played important role on the discovery of tau neutrino which is the last elementary particle out of twelve. In addition, the Nobel Prize in physics 2015 is given for the discovery of neutrino oscillations which shows neutrinos have mass. One of the last evidence of neutrino oscillation is provided by the nuclear emulsion based experiment OPERA in the appearance of tau neutrino through neutrino oscillations. A prospect of nuclear emulsion experiments foreseen in near future is discussed in this article.

Recently, high position resolution detectors for ultra-cold neutrons is necessary in studies using them. We started to develop such a detector by using fine-grained nuclear emulsion consists of silver halide crystals with their diameter of several ten nanometer and nuclides which absorb neutrons with large cross section.

In order to realize organic thin-film transistors showing high carrier mobility, it has been well recognized that both molecular structures of organic semiconductors and their packing structures in the solid state (crystal or thin film) are important factors. In this contribution, we estimate the electronics structures of several high-performance organic semiconductors by calculating the intermolecular orbital overlap of the frontier orbitals (or transfer integrals) and then correlate to the mobility reported for their thin-film transistors. As a result, despite the fact that their packing structures are not in the same type, their electronic structures can be regarded as two-dimensional (2D) system, indicating that the construction of 2D system is the key to realize high-performance organic semiconducting materials.

We report two computational studies about mechanically deformable semiconductors for flexible electronics. First we report the effect of compression and stretching of organic semiconductors estimated by molecular dynamics. Second, we present first principle electronic structure studies of hexagonal boron nitride doped with carbon.

Since organic semiconducting matrials have huge diversity compared to inorganic materials and tremendous amount of them have been reported from day to day, evaluation of charge carrier properties of organic materials could not offer sufficient answers. Under such situation, non-contact and non-destructive measurement techniques with electromagnetic wave, specifically microwave, have a potential of rapid evaluation despite they are completely based on experiments. In the present article, we introduce their theories and characteristics as well as our recent application to conduction at interface or under high pressure which could not be detected directly by conventional method.