A new type of cold/ultracold neutron detector that can realize a spatial resolution of less than 100 nm was developed using nuclear emulsion. The detector consists of a fine-grained nuclear emulsion coating and a 50-nm thick 10 B4C layer for the neutron conversion. The detector was exposed to cold and ultracold neutrons (UCNs) at the J-PARC. Detection efficiencies were measured as (0.16±0.02)% and (12±2)% for cold and ultracold neutrons consistently with the 10 B content in the converter. Positions of individual neutrons can be determined by observing secondary particle tracks recorded in the nuclear emulsion. The spatial resolution of incident neutrons were found to be in the range of 11-99 nm in the angle region of tanθ ≤ 1.9, where θ is the angle between a recorded track and the normal direction of the converter layer. The achieved spatial resolution corresponds to the improvement of one or two orders of magnitude compared with conventional techniques and it is comparable with the wavelength of UCNs.

We have been developing a neutron detector with spatial resolution of submicron by loading 6 Li into fine-grained nuclear emulsion. By exposure to thermal neutrons, tracks from neutron capture events were observed. From their grain density, spatial resolution was estimated. Detection efficiency was also measured by an experiment with cold neutrons.

We have been developing neutron detectors with spatial resolution of submicron to several tens of nanometers using fine-grained nuclear emulsion with nuclides with large neutron absorption cross sections such as 6 Li and 10 B. Those detectors were demonstrated their ability to detect cold and ultra-cold neutrons.

The Nagoya University Accelerator driven Neutron Source (NUANS) is constructed at the main campus of the Nagoya University. The electrostatic accelerator is used with the maximum proton energy and intensity of 2.8MeV, 15mA(42kW) respectively. Two neutron beamlines are designed at NUANS. The BL1 is dedicated to BNCT development. The BL2 is designed for research and development for neutron devices and neutron imaging. The neutrons used for the BL2 are generated by using the (p, n) reaction from a thin beryllium target. We constructed a compact target station for the BL2 and measured the neutron transmission image.

In this study, a high spatial resolution cold/ultra-cold neutron detector was developed using Nano Imaging Tracker (NIT), a very fine-grained emulsion, and 10 B with a large neutron absorption cross section. The detector has a 10 B 4 C layer with a thickness of approximately 50 nm. The resolution is expected to be approximately 100 nm. The detector is a powerful tool for experimentally examining gravity by using quantized states of neutrons. Our detector was exposed to cold/ultra-cold neutrons and successfully detected alpha or 7 Li tracks from neutron absorption of 10 B. Furthermore, the authors are developing an algorithm for automatic track recognition to detect those tracks.