A simple radiometer type, vacuum gauge was developed from Sandvicks radiometer. Satisfactory results were obtained concerning the absoluteness, linearity, and. reproducibility. The application of the new gauge to the measurements of final vacuum, pressure change of closed vacuum system, and chemically active gas pressures, etc. was very fruitful.

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It is ascertained, that the positive ion emission from the tungsten cathode of the ionization gauge is one of the sources of errors when the calibration of the gauge is finished under the presence of the residual positive ion emission.

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The Adsorption of water vapour on glass surfaces in vacuum has been studied. By measuring the time lag in setting up the steady state of molecular flows, one may measure the adsorption of water vapour without the influence of ion gauge.
Using high vacuum techiciques, it is possile to make the experiments with a residual gas of about 1×10^-8mm Hg, and the speed of cleen-up in Fogel type ion gauge for air is obtained. Surface areas of glass samples are determined by the B. E. T. method with ethylene adsorption. It has been estimated that the adsorption of water vapour on glass surfaces in the range 10^-5 -- 10^-6 mm Hg is not a simple physical one, and that the amounts adsorbed on lead bolosilicate glass are less than on soda lime glass.

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In this paper the authors describe some experiments on the performances of a diffusion pump. (i.) The back diffusion of the rotary pump oil toward the diffusion pump does not greatly influence to the end vacuum of a fractionating metal diffusion pump. (ii.) In the case of a large diffusion pump which backed by a small diffusion pump whose performances are the same as the former, the throughput of this pump system is limited by the smaller pump to its capable throughput. When the throughput of the system exceeds the capable throughput of the smaller pump, the operation of these pumps will sop. Then, the temperature of their boilers will begin to rise at the constant heater input, and will operate again at the optimum temperature that is higher than the normal rating temperature. Therefore, some precaution to prevent over heating the diffusion pump oil must be taken for the evacuation schedule with these series pump system of which one has larger capacity and the other smaller one.

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In the Institute of Nuclear Study, a synchro-cyclotron, which has the pole piece diameter of 160cm, is now under corstruction. This machine is designed can be also used as a ordinary cyclotron, so the dee must be frequently exchanged under the atmospheric pressure. So the vacuum system of this machine mast have excellent high evacuating speed. In this report it is described on the design factor, planing and expected performances of this vacuum system.

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An evapor ion pump using titanium wire as getter material, is now under construction.
This paper reports its design basis and something new obtained during its construction works.

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