The radiation field from a current filament is calculated. The filament is located in a homogeneous, unbounded plasma medium under an impressed magnetic field and carries travelling electric or magnetic current. We use the usual formula of the dielectric tensor of the plasma, where the temperature effect is neglected and the constancy of the collision frequency is assumed. There exist two sets of wave modes to be excited. The field from the current filament is made up by superposition of these two sets of wave modes in both cases of electric and magnetic current filaments. The approximate formulae for the attenuation length are obtained in several cases.
A load cell of frequency conversion type is described, which utilizes the piezomagnetism of Ni-Zn ferrite-the change of the reversible permeability of biased ferrite by stress. The trans-ducer is composed of a ferrite core biased by permanent magnets and a coil wound around it. The coil and a capacitor form a tuning circuit of an oscillator, the frequency of which increases 15% by the change of the permeability when a compressional load of 500 kg is applied. The out-put of the transducer is given directly in digital number and no error due to electrical circuits arises. The calibration curve is linear up to 500kg and both the non-linearity and hysteresis error are less than ±0.5%. The temperature coefficient of the sensitivity is +0.5%/°C. The zoro frequency drift is mostly due to the temperature variation and is about +0.5%/°C, which can be reduced to ±0.01%/°C with a compensation coil.
Some formulas for calculating the optical constants of a substance from Fresnel's coefficients are theoretically derived by the use of measured reflectances of the substance in two cases of polarized and unpolarized incident beams. When incident beam is partially poralized, experimental methods to eliminate the effect due to the polarization of the beam from the measured reflectances are devised. Lastly, the effect of experimental accuracy of reflectance measurements on the optical constants is discussed.
A study is made on the making of transparent and conductive film of indium oxide by vacuum evaporation. Such a film is found obtainable by heating evaporated indium film in air at a tem-perature below 150°C, the evaporation being at appropriate rate and oxygen pressure. Changes of resistivity, density and mobility of carrier, and light transmittance of the film during the transition to transparency are measured against the heating time. The amount of oxygen occluded in the film is confirmed to play an important role in obtaining the transparency.
To obtain some informations on the excitation mechanism of-He-Ne laser, a study is made on the characteristic of infrared (1.1523μ) oscillation excited by means of pulsed HF as done by Brachet et al., Petrash and Knyazev. The wave forms of the exciting pulse, laser output and spontaneous emission (near 6000Å) are observed simultaneously by the use of a dual beam syzi chroscope. The pulse form of laser output depends on factors such as the power of exciting pulse, pulse width, pressures of He and Ne and so on. It is found that the laser pulse rises with about 20μs delay, a peak of laser output occurs in the afterglow period and its height increases when the width of excitation pulse is small. The results of experiments can be explained in the main if we assume that the decay time of He 23S metastable state is about 60μs and that of the quench-ing due to Ne 1 s states is about 6μs.
Experiments confirmed the occurrence of a peak in the output at the beginning of oscillation of a He-Ne laser (1.15μ) excited by a considerably strong pulse. Delay of oscillation and decay of enhanced laser beam in the afterglow are discussed in connection with the population of, He 23S state. The magnitude of the peak, both at the beginning of oscillation and in the afterglow, and that of the plateau are measured in terms of the exciting power and its pulse width. The beam in the afterglow is found to enhance all the more when the exciting pulse width is small. As an explanation of the occurrence of peak at the beginning of oscillation, a physical picture of the mechaism is given.