Kiyoshi Sugihara

Scintillation Pulse Shapes of Anthracene Single Crystals in Nanosecond Region. I. Initial Spikes in α-Scintillation Pulse

The accurate measurement of scintillation pulse shapes of anthracene single crystals has been performed by a newly constructed device with the time resolution of nanosecond by means of the sampling method under the pulse height selection and the accumulation of pulse shapes. The distinctive differences between the pulse shapes of luminescence excited by α-, β-particles, γ-ray and UV light pulse were observed. In case of excitation of α-particle, there appeared a characteristic peak which seemed to be superposed on a scintillation peak excited by β- or γ-ray. The dependence of this faster component, that is, the initial spike on the values of d E /d x of α-particle in anthracene crystal has been studied.

Two-Dimensional Thermal Contraction of Composites

The thermal contraction of composite materials has been studied by changing the off-axis angle and the content of the glass fibers in order to analyze the thermal strain of anisotropic materials. The distributions of thermal contraction in a composite plate have also been measured down to liquid nitrogen temperature using laser speckle photography. Square-shaped composite plates were given the thermal gradient by cooling the center of the specimen. In-plane displacements were measured by speckle photography. The calculations of the strain distribution were made by a finite element method based on the off-axis angle dependence of the thermal contraction. Good agreement was found between calculated and experimental results.

Deformation Measurements of Materials at Low Temperatures Using Laser Speckle Photography Method

We observed deformations of several materials during cooling down process from room temperature to liquid nitrogen temperature using the laser speckle photography method. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacement gradients by the defocused speckle photography. The results of measurements of in-plane displacement are compared with those of FEM analysis. The applicability of laser speckle photography method to cryogenic engineering will also be discussed.

A Light Pulse Source of a Few Tens of a Picosecond to Nanosecond Width with Cherenkov Radiation

It was experimentally proven that Cherenkov radiation arising from intense electron pulses passing through a dielectric material could be utilized for a light source of short pulse width. A linear accelerator at ISIR, Osaka University, which can produce intense single-bunch electron pulses, was used for a Cherenkov radiation exciter. The spectral distribution and pulse shape of the Cherenkov radiation from an air radiator with these electron pulses were investigated with a fast detection system for this purpose. The spectrum showed a peak at 200 nm and a continuous band of which intensity decreased towards the longer wavelength. The minimum pulse width of the Cherenkov radiation with the single-bunch electrons was about 40 ps, and the light peak power was about 10 kW in the spectral region of 200 to 600 nm.

Measurements of Photostimulated Electron Emission from Superconducting Metals at 9–300 K

PSEE measurements for superconducting and other type metals were carried out between about 9 and 300 K. Electron emission decreased upon lowering the sample temperature to that of liquid N2 and showed two peaks in the course of the temperature change. One was attributed to residual gas adsorption and the other to sample deformation. PSEE yield did not change at the transition between the normal and the superconducting states.

Fracto-Emission from Crystalline and Non-Crystalline Materials at Cryogenic Temperatures

Electron emissions from metals, FRP and ceramics during the fracture process (fracto-emission) at cryogenic temperatures have been reported in previous conferences. In this paper, the FEs from some crystalline (single and poly-crystal) and non-crystalline (glassy state) insulating materials are compared and discussed. The FEs from sodium silicate glass and pure fused silica are very similar to those from poly-crystalline ceramics, but are different from those from synthetic quartz (single crystal) especially for fracture at room temperature. From experimental results, the fracture modes, generation of free electrons and its compensation in these materials are discussed.

Fracto-Emission from Ceramics at Cryogenic Temperatures

Electron emissions from fine ceramics of alumina during the fracture process (fracto-emission, FE) at cryogenic temperatures were observed and compared with those from brittle metals, glass and single crystals of SiO2 etc. The features of FEs are intended to be classified in metals and insulators, and moreover, the latter are into single and poly-crystals, and non-crystalline (glassy state). However, the FEs from alumina ceramics of polycrystalline are very similar to those from sodium silicate glass and pure fused silica, but are different from those from synthetic quartz (single crystal) especially for fracture at room temperature. From experimental results, it is supposed that they depend on the fracture modes, fracture strength and electronic properties for generation of free electrons and its compensation on fracture surfaces of these materials. These problems are discussed here.

Fracto-Emission from Glass Fibre Reinforced Plastics at 170–200 K

Tensile tests for glass-epoxy composite materials have been carried out at low temperatures in order to examine various relations among electron and acoustic emissions and the load-elongation curves of composite materials. Deformation and fracture processes are discussed on the basis of experimental results. The effects of the reinforcement direction on the materials are also examined.