Basic data of radiation thickness gauge are given. The effect of distance between Co60 and iron plate and their geometrical arrangements are experimentally determined to obtain optimum conditions. Effective scattering area is also determined and measurable maximum thickness, which is limited by the saturation of back-scattering, is achieved to be extended to 25_??_30mm by properly shielding the scattered rays from thin portions of the plate. Theoretical considerations on the design of the chamber most sensitive to scattered γ rays are given, 4mm for the wall thickness and 4 atm. pressure for the inner gas are found optimum for 70×70×200mm chamber size used in the experiment. The practical thickness gauge “Reflectron” is now being manufactured and in service in S Chemical Co's plant. Description of the apparatus in detail and data on various materials and backings will be reported shortly.
Although there are many accurate methods of measuring the time interval, they are not ideal for the use in physical training or physiological observations. Improved chronographical method is described in which the signal is operated by amplified photo-electric current instead of by the customary electro-magnetic or spark device. Graphical studies of the signal are made and a utility model is constructed with which the time interval is measured with the accuracy of 1/100_??_1/200 second.
Alundum is usually used as coating on heaters in vacuum tubes for insulation. But alundum, when heated, becomes semi-conductive causing a current to leak through the space between the heater and the cathode often originating hum of the tube. This paper deals with several causes of current leak involved in the processing of tube production. 1). By heating, BaSr(CO3)2 on cathode gives out CO2 or CO by dissociation, and if the gas pressure is higher than 0.1mmHg, CO2 or CO is further dissociated to O2 and C. The carbon produced is deposited on the surface of alundum and diffuse into it thus incresing the leakage current. 2). By applying high voltage to the alundum layer, the conductivity becomes higher by the increase of the number of elecrrons excited thermally to the conduction band resulting in eventual increase of the leak. 3). With D. C. voltage on the alundum layer at a certain temperature above some 1250°K, thermal breakdown takes place. The breakdown voltage is lowered by the rise of temperature but is raised by prolonged aging- The pulsive breakdown voltage is always higher than D. C. breakdown voltage and depends upon the duty cycle.
Crystal structure of selenium film deposited on well polished Ni surface in vacuum under the following conditions are investigated. 1) The degree of vacuum: 10-4mmHg. 2) The base temperature: a room temperature-173°C. 3) The thickness of film: 0.1μ_??_10μ. 4) The speed of evaporation (the quantity of selenium vapor evaporated from crucible): 1_??_6mg/min, 0.1g/min and 0.3g/min. The results are shown in Tables 1 and 2. The structure of the film depends on the thickness, the temperature of the base and the speed of the evaporation. Structure of the first layer is either fibrous or of random orientation depending on the condition. Subsequent lavers are spiral-fibrous and ring-fibrous.
An apparatus of spherical shell type of the radius s of a few mm having uniformly distributed point heat sources on its surface is used for measuring thermal conductivity. The thermal conductivity is given by the equation k=q0/4πθ·1/s_??_ on the assumption of no heat loss, Θ∞ being the temperature rise of the center of the shell after infinite time, q0 the heat input per unit time. Correction for the heat loss through the lead wires of the heater and thermocouples is performed by the equation k_??_k+b√km, where km is the thermal conductivity by the aforementioned equation assuming no heat loss, k the true conductivity and b a certain constant of the apparatus. This equation is derived by the condition of heat conservation q0=ql∞+q∞ at infinite time where ql∞ is the heat loss through leads and q∞ the heat input to the shell, both per unit time.
In order to deal with the phenomena in semi-conductors, following hypotheses are introduced: 1) Besides excitations caused by light and heat, excitation by collision between the carrier and the lattice occurs comparatively easily, the chance of which being in proportion to the density of electric current. 2) When a portion of semi-conductor is excited, the potential of that portion becomes higher for the majority carrier than the rest of the semi-conductor. According to the above hypotheses, physical explanations of the “hole injection” and the “surface barrier” are attempted. They make it possible to give a unique and consistent interpretation of the working mechanism of such as crystal diodes, metal rectifiers and transistors. A model for the blocking layer of metal rectifier is worked out and experiments are made for its verification.
In a former paper, an automatic apparatus using inclination method for measuring static friction was described. In the present paper, another one of new type is presented in which horizontal driving method is adopted in order to maintain normal load perfectly constant during the whole period of operation. Some examples of static friction coefficient are given in comparison with those obtained by two other methods.