A review is given on recent progresses in dosimeter with silver-activated phosphate glass. Trapezoidal shape of glass and its cell combined with a suitable holder greatly improves the dosimeter energy response to β-rays and to X-rays down to 20 keV. The glass dosimeter response to thermal and fast neutrons is described. Fast neutron dose can be measured from the Cerenkov radiation intensity due to 31P(n p) 31Si reaction in the glass. An improved spherical capsule makes the glass response independent of photon energy and its direction. A standard glass washing method and the increase of mechanical and chemical stability of dosimeter glass are described. With a scanning method we can measure energy and direction of incident radiation. A simplified scanning method for glass encased in spherical capsule is described. Glass encased in a half spherical capsule serves for reading the dose of frontal or backward radiation at our critical organs by the scanning method. How to obtain a good performance of glass dosimeter for routine personnel dosimetry and long-term environmental monitoring is described. We have recently succeeded in developing a methoded with UV laser pulse for exciting the glass which enables measurement of 1 mR and a remarkable decrease of soil effect on glass.
In a neutral gas, a shock wave occurs as a result of particle collisions. In a high temperature plasma, ions and electrons have very long mean free paths, but their gyro-radii are small. Therefore, a shock wave in a high temperature plasma, that is in a collisionless plasma, is formed by a quite different mechanism from that in a neutral gas. In a collisionless shock wave, the dispersion plays an important role in the formation instead of the dissipation in a collisional shock. A typical wave in a cold collisionless plasma is a solitary wave which is unstable for perturbations and shifts to a quasi-shock wave as a result of thermal motions. Analytical methods for collisionless plasmas are classified into two. In one method, the governing equations of the elliptic type are transformed to equations of the diffusion type. In the other, Vlasov equations themselves are employed.
As a result of a series of experiments carried out on the dielectric properties of butter at our Institute the following data have been obtained. The dielectric constant ε' of butter decreases with the increase of frequency ranging from 30 Hz to l kHz, is constant between 1 kHz and 1 MHz, and decreases again above 1 MHz. The dielectric loss ε" decreases from the maximum value of 0. 5 at 30 Hz, takes the minimum between 1 kHz and 1 MHz, and increases above 1 MHz. The dielectric constant e' also shows a logarithmic increase with the increase of moisture content. Furthermore, the dielectric loss ε" depends upon temperature at frequencies below 30 Hz and above 1 MHz. There are two peaks of dielectric loss at the temperatures of about 5 and 10°C respectively and the correlation between ε' and ε" at various temperatures can be represented by Cole-Cole's law. The relaxation time z and activation energy ΔH are 7. 96 sec. and 11. 6 kcal/mol respectively at temperatures ranging from 0 to 5°C and 6.30 sec. and 28.3 kcal/mol from 5 to 20°C.
(Bi1-xSbx)2(Te1-ySey)3 compound were prepared from melts with stoichiometric composition by the quenched technique and annealed in a vacuum at 400°C for 10 hours. The temperature factor of crystals in the whole range of hexagonal structure was determined by X-ray powder mothod and estimated to be 1. 8_??_4.0 Å2. The contour map of the temperature factor has two peaks (maxima). The thermoelectric figure of merit Z(=α2σκ-1) and lattice thermal conductivity κg(=κ-LσT) were measured in these materials and are found to be related with the temperature factor of crystals. Futhermore the following equations are obtained in the hexagonal structure region κg=A1•Ma-(1/2)B-(3/2)•δ (W/deg•cm) Z=A2-Ma(1/2)B(1/2)•δ-2 (/deg) where An: constant, Ma: atomic mass, δ: atomic radius.
Thin metal foils of Cu, Al and Sn were electrically exploded by capacitor bank discharge (maximum energy; 1500 joules, ringing frequency; 70 kHz) to accelerate a thin plate projectile (flyer). Dependence of the flyer velocity on the foil thickness, capacitor voltage and shock transmitter thickness were studied. It was found that the flyer velocity is almost constant, irrespective of the kind and thickness of metal foils employed, if the calculated value of foil vaporization energy does not exceed a value equal to about 15% of the capacitor discharging energy. Spall experiments of polymers, glass and ionic crystals were made using this explosion system. In view of fracture morphology some interesting phenomena associated with the heal of crazes and cracks were observed. It is noteworthy that in spite of the low discharging energy delivered by the present apparatus the apparatus proved to be sufficiently useful for the study aimed.
Quantitative electron probe microanalysis for the precipitates in bulk material or the thin film located on substrate is not easy, because an X-ray spectrum from the irradiated volume contains not only the component from the precipitates or the thin film but also the complex components from the matrix surrounding or underlying them and it makes the determination of the chemical composition of the precipitate or thin film difficult. This paper presents a utilization of the absorption edge characteristic of the constituent elements for making a reliable quantitative analysis on such a kind of specimen. It is shown by some experimental results that the composition of the precipitates or the thin film can be determined directly without any confusion from the influence of matrix elements.
β-SiC crystals were grown from Si melt in a carbon crucible at about 1550°C. By the use of a crucible with a brim, fairly large crystals were obtained. The crystals obtained were needle, ribbon and plate in shape, and a typical ribbon form crystals were about 4×1×0.05mm3 in size. For the purpose of obtainning high purity crystals, a double-wall crucible was used. This type of crucibles was composed of an inner wall made of high purity carbon and an outer wall made of high density carbon. Photoluminescence related to Ill b acceptors were not observed from the crystals grown in the double-wall crucible. Red luminescence of a unknown origin was observed from these crystals. This red luminescence was greatly reduced for the crystals doped with boron in concentration of about 10-5 at%.