The impedance of a semiconductor wafer inserted in a waveguide is studied theoretically and experimentally. The real part of the impedance becomes maximum when the ratio, η, of the displacement current to the conduction current is unity; at this instant the microwave angular frequency becomes equal to the reciprocal of the relaxation time, τ0, for dissipation of charge density. At the frequency of 9 GC/sec, the real part is maximum for Ge of 13 Ω-cm and for Si of 17 Ω-cm. The resistance part of the impedance decreases gradually, while the reactance part approaches to a constant value when the displacement current begins to dominate at higher resistivity at which the microwave period is shorter than τ0. At η=1, the normalized imaginary part of the impedance as a function of frequency is maximum and the normalized real part is equal to 0.5. Experimental results at 9 GC/sec agree fairly well with the theory.
Two kinds of hysteresis are observed on curves of oscillation power expressed as a function of bias voltage of a tunnel-diode microwave oscillator. The oscillator is of a straight 2/4 strip trans-mission line resonator of the frequency of about 1.6 Gc/sec. One kind of the hysteresis resembles the one usually observed in a low frequency region; it can be quantitatively analysed by nonlinear static characteristics of the tunnel-diode, analogous to the hysteresis at low frequencies. The other kind of the hysteresis, which occurs weakly at a lower bias voltage with a linear characteristic, can be explained by a drift of the junction temperature during the operation.
A spark discharge tube of Weissler's type which can be used as a light source in the vacuum ultraviolet region has been constructed. After a brief summary of what is generally required for the light source in this region and a discussion on how the Weissler spark differs from the Lyman spark, the design and construction of the apparatus are described. The spark tube comprises a quartz capillary tube of 2.8mm in inner diameter and 60mm in length separating the electrodes, a ceramic tube carrying the anode and an independent cathode section which is of Worley's type. Intermittent, 100 times a second, discharges go through a capillary filled with a mixture at about 0.1 mmHg of helium and a small amount of N2 or argon. Intensity distribution of the observed spectra which covered the range from 450Å to 2000Å is examined under various conditions of the exciting power, the pressure, the composition and the relative abundance of the component gases, with particular intention of obtaining the optimum condition in which the intense signals are obtained in the region _??_ω>15eV (λ<800Å). The stability, the noise, the life, and the contamination of optical systems arising from sput-tering of the electrode materials are also considered.
A simple gate circuit with only one diode is devised. Differed from other gate circuits, this circuit is conditioned to operate with the gate pulse height exceeding the maximum level of the gate pulse but not necessarily being fixed. Since small fluctuation of the gate pulse is not import-ant as long as the pulse height remains larger than the level, construction and adjustment of the gate pulse generator are simple; moreover, no power supply is necessary for the gate. The maximum single rejection ratio 23:1 of output pulses of the gate and the linearity tested by the use of pulses of gamma-rays from Cs137 (0.662 MeV) and Co60 (1.17 and 1.33 MeV) are found satis-factory for the present requirements.
Structural changes associated with outward diffusion of zinc in single and poly-crystals of a brass are studied by metallographic and X-ray techniques. The dezincification is carried out in a vacuum at high temperatures. The results observed in the diffusion zones are. summarized as follows: Great numbers of dislocations are produced in the diffusion zones by plastic deformation and vacancy condensation. A large amount of slip is caused near the free surface of the specimen, which is clearly observable at low diffusion temperatures. Density of dislocation and fineness of the sub-structure are higher near the free surface than in the inner part. These structural changes result from generation and subsequent redistribution of dislocations by slip and rise during the diffusion. Some of the aggregations of dislocation etch-pits in the diffusion zones indicate that some dis-locations are formed from the vacancy condensation. In the case of single-crystal specimens, specially orientated voids are seen developed in the diffusion zones at high temperatures and during long diffusion time, the voids developing along a particular lattice plane. It is concluded that the dislocations produced by plastic deformation and vacancy condensation during the dezincification can behave to accelerate the outward diffusion of zinc. Furthermore, present results substantiate both theories of Brinkman2) and Balluffi2) that a tensile stress arises and a state of vacancy supersaturation exists in the diffusion zones suffering a net loss of atoms.
The distant propagation of light in connection with the distant communication by laser light is discussed. As a model of the field with the extent a and the radius of curvature of wave front l, _??_ is chosen. When the light covers she distance z, the field uP becomes _??_ This leads to that the position at which β becomes minimum is not the ordinary focus because of the large effect of diffraction by the aperture. The values of a and l, which make the loss minimum in transmitting. the light through a pipe of the linear dimension φ over the distance D are obtained and a discussion is made on an appro-priate relay optical system.
By examination with a Twyman interferometer, a perfectly homogeneous block of barium crown glass of 0.5 wt% Nd2O3 content is obtained. On five cylindrical laser rods of 5 mm in diame-ter and about 5cm in length each, cut out of the block and passed muster, their near-and far-field radiation patterns are examined, and several characteristics-granular appearance of near field and direct patterns, ring-type emission patterns near the threshold and their relation to directionality, and others-that are found inherent in homogeneous glass laser rods are discussed in detail.