A gridded ionization chamber has been constructed; its saturation characteristics, energy resolution, and the pulse-height-versus-energy relation and performance of electronic circuits are determined.
The energy resolution of 60 KeV in half width was attained for a 6 MeV peak; r.m.s. noise in this case (about 500 in electronic charges) was 20 percent larger than the calculated value.
Both the saturation value of the pulse-height and the energy resolution were found to depend on the pressure of gas in the chamber.
Pulse-shape and pulse-height analyses of grid-signals are made as a preliminary test for possible applications of grid-pulses to electronic collimation and measurement of angular distribution of (n, α) or (n, ƒ) reactions. In particular, a “double-grid” arrangement is tried to eliminate the undesirable capacitive coupling between grid and collector.
With the chamber, a study of air-borne radioactivity is made. The concentration of Pu-239 in 1957 at Tokyo was determined to be at least 10^-20 curie/litre.
Also, the Q-value of the N¹⁴ (n, α) B¹¹ reaction is measured, with special attention to the pulse-height vs. energy relationship at lower alpha-energies. The Q-value obtained was in a better agreement with the current mass-Q-value than that found by previous authors. Furthermore, drift velocities of electrons in argon gas are determined from the pulse-shape.

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The yield of X-rays, that is the mean number of X photons produced by a β-particle, is determined. The intensity of X-rays having an energy greater than 10 keV from a β-ray source such as ³²P, ⁹⁰Sr-⁹⁰Y, or ²⁰⁴Tl combined with a target is measured with a NaI(Tl) scintillation spectrometer. The detection efficiency and the energy resolution of scintillation counters are also measured. The relations between the X-ray yield on one hand and the target arrangement and thickness, atomic number of target materials, β-ray energy and KX-ray intensity on the other are examined.
The results obtained are as follows:
1) The maximum X-ray yield is obtained with a thin front target and a sufficiently thick back target.
2) The X-ray yield with a target of thickness 1mg/cm² is nearly proportional to the atomic number of the target material and to the square of the mean β-ray energy.
3) The purity ratio of KX-ray observed can be made to increase by the use of a thin NaI scintillator.

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Cold-cathode type X-ray tubes with auxiliary triggering electrode are developed which can produce X-rays of sufficiently high intensity with short duration of the order of one μ sec. To. get fine definition in the photogram, the anode of conical shape is used, and the most efficient condition of gap length between cathode and anode is investigated experimentally.
By means of this X-ray apparatus combined with some suitable electronic delay circuit (3μ sec_??_10m sec) for triggering, X-ray shadowgrams corresponding to various stages of electrical explosion of fine metallic wires (fuse metal, copper, steel etc.) and thin aluminium foils are studied.
When the electric current density through the wire is small, it is observed that, some-undulatory deformation of the wire takes place, resulting to the splitting of the wire into many fine droplets. In the early stage of explosion of copper wire coated with tin, its length is greatly increased and takes irregular zig-zag form, while its diameter remains the same as original. If the electrical energy in the wire is sufficiently high, sudden explosive vaporization occurs without any undulatory deformation or droplets formation.

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Intensity of electron diffraction beam is measured by a scintillation counter in combination with a pulse height analyzer and other counting appliances. For measuring electron beams of 10 KeV_??_50 KeV energy in vacuum, plastic scintillation counter is found most suited. This counter coupled with a 931A photomultiplier is used to obtain relation between pulse height and electron energy in the above-mentioned range. For monoenergetic electron beams, the peak of pulse height distribution curves was located with error of a few percent, but the energy resolving power, that is the ratio of half width of the peak to the pulse height voltage at the peak was 15%. Measure-ments made with this setup on the intensity of diffracted beams from evaporated Al and Au thin foils under various channel widths and discriminator voltages of the pulse height analyzer proved the superiority of scintillation counter method over photographic and d.c. amplifier methods both in intensity measurement and energy selection. Results of experiment are discussed.

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The excitation spectrum of phosphor is of special importance from theoretical and practical viewpoints. For a long time, the wavelength dependency of the ratio of fluorescence intensity of powdered phosphor to excitation intensity has been an object of interest called the excitation spectrum of powdered phosphor. The ratio D of fluorescence intensity to excitation intensity, however, is varied in its absolute value and significance by not only the inherent characteristics of the phosphor but the experimental condition.
This paper deals with the excitation spectra of powderd phosphors when used for fluorescent lamps in which, because of multiple reflection on phosphor walls and of wavelength dependency of spectral reflectance of phosphors, the distribution of excitation energy and the absorption on phosphor walls are different from the case of single reflection.
From the results found on the absorption coefficient of powdered materials and the absolute value of the ratio D, and by assuming appropriate values of scattering constant and thickness of phosphor wall, excitation spectra of several phosphors are calculated. In this calculation, the end effect of the lamp given by P. Moon's equation, the non-linearity of D value in respect of excita-tion intensity and the possible change in quality of the phosphor during coating process are ignored.
With the scattering constant of 210 cm^-1 and the thickness of layer of 3mm, the D value was found to increase when the reflectivity of phosphor is smaller than 0.5 but decrease when it is larger than 0.5.

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This is an extensive study of the electrical copper deposit technique for measurement of defects in metal alloy junctions in germanium. These defects are formed during the process of recrystali-zation for two main reasons: one of these growth are dendrite and the other are inclusion of primary defects such as blow holes. The electrical characteristics of these contacts show linear voltage-current relationship as well as large saturation current. This is explained in' terms of a low and distributed value of breakdown voltage and of the current limiting property of spreading resistance attached to each breakdown spot. Distributed value of breakdown voltage are observed at liquid nitrogen temperature.

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High sensitive and stable CdS photoconducting films on fused quartz plate are obtained. Sintered films of about 10 μ in thickness can be prepared by simultaneously adding impurities and sintering with CdCl₂ as the flux. Effects of impurities on optical and electrical properties of the films are investigated. A sintered US photoconducting film with a large photocurrent (above 1 mA), a small dark current (below 1 μA) and a small time constant (about 10 m sec) was obtained by adding 0.05_??_0.1 atom % Cu in CdS and 0.2 mole CdCl₂ in 1 mole CdS. Small variations of photocurrent and dark current with temperature ranging from 0°C to 80°C were observed. The sintered CdS photoconducting films had little change in photoconductivity over a period of one year.

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