The availability of X-rays excited by 90Sr-90Y betas in lead target for technical radiography is studied. The β-excited X-ray source consists of 90Sr of 80 mc and lead target of suitable thickness to produce X-radiation. The energy spectrum and the dose-rate distribution of the X-ray source are observed, and exposure charts for radiography are made with the use of step wedges of steel and aluminium alloy. X-ray energy spectrum is a continuous bremsstrahlung curve up to 500 keV with the peak in 74 keV of PbKX-rays, and the X-ray intensity was about 10mr/h at the distance of 30cm from the front of X-ray source. The radiographs, obtained with the β-excited X-ray source, show good definition in spite of the fact that the active volume is great (3mm diameter and 8mm long), and indicate that 90Sr-90Y β-excited X-radiography can be used for steel of thickness up to about 3cm.
It was reported that the light pulse produced by monoenergy electrons impinging on anthracene crystal is proportional to the electron energy within its limited range. In the present work, the response of a large single crystal of anthracene to impinging β-rays emitted by radioactive substance is discussed. The crystal used is of cylindrical shape, approximately 2.5cm in dia. and 3.0cm in height. It is glued with silicon grease to the photocathode of DuMont 6292 photomultiplier tube. Output signals are proportionally amplified by an Al type linear amplifier and are analyzed by a single channel pulse height analyzer. Spectrum of β-rays from a pure, β-emitting substance, such as 35S, Ra D, E, F or 90Sr+90Y, is observed and compared with that obtained by a lens type magnetic β-ray spectrometer with the result that the two spectra are similar except in the low energy part where the intensity by the former is higher than by the latter. This seems attributable to both the bremsstrahlung by β-rays and the imperfection of the crystal which was coloured and opaque. Relation between the maximum energy of the β-rays and the pulse height is of good linearity from 0.16 to 2.2 MeV of electron energy.
Xe-proportional counter and NaI-scintillation counter are compared in regard to detection efficiency and monochromatization effect when used with X-ray diffractometer. The comparison is made first in the intensity of spectrum of X-rays from a Cu-target X-ray tube operated at DC 30 kV and analyzed with a calcite crystal. Width of the window of pulse-height analyzer is made to be set for assigned percentages of CuKα. A Ni-filter, 20μ thick, is employed. The intensities measured are corrected for the variation of reflection coefficient of calcite with wavelength. The ratio of the total intensity of continuous radiation to the intensity of CuKμ was about 6% with the proportional counter and 16%_??_11% with the scintillation counter, and the respective detection efficiency was about 20 and 35%_??_25%. This ratio with balanced filters on the scintillation counter was about 2%. As to the monochromatization effect, either one of the counters with pulse-height analyzer alone does not satisfy the requirement in accuracy for exact diffractometer work.
Characteristics of the U-scope Patterns in general and some special characteristics of Simple and Compound patterns by isolated point sources of radioactive substances are almost perfectly solved in the previous paper, -No. 7, Vol. 27, 1958 of the Journal of Applied Physics, Japan-with many illustrations and there a response function η performed an excellent role in the explanation of the constitution of these patterns. However, Diffused or Background Pattern by diffused sources, for example, by outcrops of granitic rocks, and scattered sources, for example debris of stone frag-ments and gravel on the road, cannot be explained simply by the response function mentioned above. To make it possible to solve these complicated problems the following three concepts are introduced: i) Substitution of equivalent radioactive surface charge on the outcrop for the actual source. ii) The integral response function Y=∫2α-2αηdφ, and iii) The fundamental formulae for the calculation of responsibility of U-scope for scattered sources of radioactivity. This way of conducting the analysis is well supported by the outcome of discussions concerning the experiments carried out at Tokai, the Lake Biwa, and at the Bay of Kojima in March of this year.
The flexible mirror of a pneumatic cell is the important part that affects the sensitivity of the cell. The mirror involves two main factors: the tension and the reflectivity. The performance of the cell becomes the better, the weaker the tension and the higher the reflectivity, but the weakening of the tension by reducing the mass of evaporated metal would result in the lowering of reflectivity of the mirror which in turn lowers the gain of the optical system. The detecting sensitivity is thus represented by the product of the said two factors, each of which is governed by the thickness of the evaporated metal film, suggesting that there are optimum conditions assigned to the mirror as enumerated below. 1) The most favourable thickness of the collodion base film is 50mμ_??_100mμ for the tension of about 3100 dynes/cm. 2) The tension of the mirror for practical use is of the order of 104 dynes/cm which corresponds to the restoring power of about 105 dynes/cm. 3) The ambient temperature affects the tension, weakening it by about 200 dynes/cm per degree rise of the temperature between 5°C and 15°C. 4) The reflectivity of the mirror increases rapidly with the thickness of evaporated antimony film until about 20mμ, approaching thereafter gradually to 65% as the film thickenss. 5) The optimum thickness of antimony film on the flexible mirror is about 20mμ provided that the transmitted rays do not disturb the gas temperature.
Expression for the electric potential within a box shaped conductor is sought theoretically with the source- and sink-points at the respective centers of the opposing end faces. The potential is expressed approximately by a series. By reducing the problem to two-dimension, a rectangular sheet of metal is treated for which the equipotential lines are traced by numerical calculation. A case of a thin rectangular Cd film with a Ag plate attached to each of the opposing edges is given, the source and the sink being at the respective centers of the Ag plates.
A method of measuring the surface temperature of moving bodies without touching the surface is devised. The thermometer consists of a thin thermo-couple placed at the center of a rounded groove formed along the center line of a sheet of copper which is held on one face of a small rectangular frame. The other face of the frame, opposite the back of the groove, is covered by a plain sheet of copper which can be heated uniformly by an electric heater, its temperature being measured by another thermo-couple. The interior surfaces of these copper sheets and the groove surface are gold plated, the rest parts being coated black. This contrivance with the groove side as the front is placed near the body of which the surface temperature t°C is to be found. Let the temperature of the plain copper sheet be θ°C and that read by the couple in the groove be τ°C. Then t _??_ τ _??_ θ, and if the temperature difference t-θbe small enough, it will become proportional to τ-θ, that is, the relation between τ and θ will be linear represented by a straight line on a graph with τ and θ as coordinates. The temperature t°C is then indicated by the intersection between this straight line and the straight line θ=τ. The temperature t°C can also be obtained on a graph with and τ-θ as coordinates.
A method of measuring the metallic diffusion is established by using an autoradiograph. Several difficulties encountered in using this method are overcome by contemplating that: 1) Effect of γ-rays is negligible for specimens of less than 0.2mm in thickness. 2) Photographic density on nuclear plate is proportional to diffusing atoms so long as the density is below 1.0. In this experiment, however, the density is limited not to exceed 0.5_??_0.7 (plate density inclusive) for obtaining better results. 3) For measuring photographic density by micro-photometer, the width of the slit should be set according to the penetration depth. For example, should the allowable error be 5%, the slit width would be 100μ for 1.3mm, 10μ for 0.7 mm and 5μ for 0.4mm etc. of the penetration depth. By the above method, the diffusion coefficients of a f. f. c. single crystal are determined with accuracy better than by any other method. Furthermore, anisotropy of diffusion is observed.
The electro-optic effect in. crystals of class Vd such as ADP can be used for modulating or shuttering light beam, but birefringent nature of the crystals limits the angular aperture. If crystals of class Td are available, this difficulty is overcome, and the construction of a light modulator with a large useful angular aperture becomes possible. ZnS or CuCl are crystals of Td class with a large electro-optic effect, but it is very difficult to grow large crystals by artificial means. The electro-optic coefficient of zincblende, which is cubic-ZnS in nature, is measured by using Senarmont compensator method for various wavelength, and the application to light modulator of wide aperture is experimented. The electro-optic coefficient of ZnS crystal is 5.9×10-8cm/statvolt at room temperature and wavelength of 546mμ. The voltage for obtaining half-wave retardation As about 10 kV.