In the previous paper, we reported many experimental data as to the various properties of the 32″ oil diffusion pump, which was to be used as a main pump of 63″ Cyclotron in the Institute of Nuclear Study, University of Tokyo. In this paper we tried to analyse some parts of those results and gave some discussions about pumping mechanism.
According to Jäkel, maximum pumping speed Sm is given by
Sm=v/4 1/1+1/4 v/u (1)
per unit area, where, v is mean speed of thermal agitation of gases and u is velocity of oil jet stream. Using this formula, we obtained a constant value of about 120 m/sec as a value for u from our data which were obtained for air, hydrogen and helium gases respectively. It appears to show very good agreement of the theory with the experiment.
However, in the formula (1) the terms including diffusion constant are neglected. In the original form Jäckel gives
S=v/4 1-n_g (L) e^-u/DL/1-1/4 v/u (1-e^-u/DL) (2)
=v/4 1-n_g (L) /n nf (0) /nf (L) /1-1/4 v/u (1-e^-u/DL) (3)
We assured from our experiments that one could not neglect the concerning term in the expression (3), and taking this form, Sm resulted in negative value.
Accordingly, we consider, that the replacement of (3) with (4) is not correct in general. But assuming that the diffusion constant D is negligibly small in the oil jet stream, we can obtain the formula (1) directly. and this assumption is more plausible.
We calculated also the boiler pressure from electric power consumed in the heater and compared this value with the result of direct measurement. They show good agreement. And this gives one half of the value which is expected through the experience for the pumps of smaller type.

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Recently Dr. Jaeckel reported about the pumping speed that is affected to the oil vapour velocity.
Concerning the measurement of vapour velocity it is already researched by Dr. Jaeckel and Dr. Tajima, but the author used the calculation method applying the difference of vapour enthalpy.
The author noted the special consideration to the effect of thermal radiation that affect to the temperature measurement of jetted vapour.
There are some difficulties to the correction of the temperature rise caused by the friction heat of high speed gas flow, but the measurement of relative vapour speed can be easily done by this method.

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In order to determine the sub-standard ionization gauges, many factors influencing the sensitivity of the gauges were investigated in detail.
For the calibration of the sub-standard gauges with the standard McLeod gauge, it is required that the deviations of the sensitivity is within one per cent in the pressure range of 10^-4 to about 10^-3 mm. of mercury.
Experiments have been carried out under many conditions.i. e. changing the values of pressure, sorts of gases, electron currents and potentials of electrodes, for several types and dimensions of gauges. In these experiments, we obtained an optimum condition for a gauge having sensitivity constancy for pressures up to 3×10^-3 mm of mercury while we found such an unfavourable phenomena that the stability tended to decrease slowly during five to twenty-five hours after the outgassing procedure of electron bombardment.

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A small standard leak was constructed utilizing the Permeation of probe gas through the Silicon rubber sheet.
As the leak rate of our standard leak is determined by the area and thickness of the rubber sheet, we can make a leak smaller than 1×1O^-7mmHg l/sec easily and surely.

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Metal valves available for ultra-high vacuum were produced according to the original design af Alpert and examined by a helium leak detector. Inverted type ionization gauges known as a Bayed-Alpert gauge were also made its characteristics were measured in detail. Using the above equipments an ultra-high vacuum apparatus was constructed. The vacuum of 10^-10mmHg could be readily obtained by two or three hours baking and outgassing of ionization gauge. However, the highest vacuum achieved was not so good as reported by Alpert, because of the incomplete outgassing of the system.

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The adsorption of water vapour on lead borosilicate glass has been studied at pressure region of 10^-6mmHg by using the modified flash filament technique. The adsorbed amount and the kinetics of adsorption could be obtained by measuring the variation of pressure after rapid heating and cooling of the sample, and the apparatus used in this technique was the Beeck's calorimeter type cell in which the wire of resistance thermometer was employed as a heater. The sample glass was crushed to powder finer than 200mesh and coated on the inner wall of the cell. Using this method, it was possible to measure the physical and the activated adsorption separately.
The results showed that the adsorbed amount by the physical adsorption at 10^-6mmHg, 050°C was 0.10.4% of monolayer, and the heat of adsorption was 11Kcal/mole. Most of the physical adsorption began below 50°C and the desorption occurred by heating at about 100°C150°C or by evacuation. With regard to the activated adsorption, the activation energy of adsorption was 9Kcal/mole and that of desorption was 1340Kcal/mole.
The residual gas pressure was about 510^-9mmHg and the variation of pressure was measured by a sensitive (5×10^-8mmHg/div.) Pirani gauge.

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