Life of copper-beryllium secondary emission surfaces treated under various oxygen pressures and temperatures was investigated as a function of primary current density. Changes of secon-dary emission characteristics such as yield curve, saturation curve and primary current on yield were observed at several intermediate states of life. With further observations by electron microscope and electron diffraction camera, it was thought that the dissociation of beryllium oxide film on the alloy surface by the primary electron bombardment might be the main factor to determine the life.
In modern radiography, mA-sac meters are commonly used to measure the amount of X-ray exposure which is the product of the tube current and the time of application. It has been thought almost impossible to eliminate the tau-characteristics (the strong dependency of indica-tion upon the time) of common mA-sec meters of ballistic type as they are used in wide range of time, overstepping the axiom of ordinary ballistic galvanometers. Instantaneous exposure as required in X-ray cinematography and stereo-photography made the realization of accurate integrators imperative. The author describes the developement of a theory and technique leading to the realization of deviation-free integrator (Fig. 6) and, at the same time, discussions on integration network which exhibits a high grade of accuracy of the third order of precision (Fig. s 13 and 15) and has an attractive behaviour of the indication memory for a long time. To calibrate the meter in absolute units, the author constructed a simple cybernetics system (Fig. 9), nervous system of which displays the power of quick and correct calculation and of good memory. High accuracy in radiographic technique is thus expected.
A β-ray back scatter thickness gauge of ionization chamber type having a compensating screen is described. By employing this screen, the effect of the variation of distance between the gauge and the specimen surface on the reading is reduced to less than 1%/mm for an ordinary working position. This method is therefore suitable for continuous measurement of thickness of running foils during rolling. As the sensitiveness, this method is superiorer to the transmission method up to the foil thickness of 120μ for Al.
Lack of reliable method for calibrating the depth of hemocytometer was rectified by the use of optical interferometers. Relative variation of the depth was determined with multiple-beam interferferometry in clear and accurate way. Absolute value of the depth was measured with Michelson interferometer using zero-order fringe of equal thickness, the accuracy being about 1 micron with precision screw.