Shinku

Evacuating system of ETL mass spectrometer has been designed and constructed. In designing the system several points were considered so as to obtain the pressure in the analyzer tube below 1 ×10^-m Hg and to keep the pressure constant. On the basis of the inquiry, following specifications were adopted : analyzer tube, all stainless steel ; evacuating system, two 4″ diffusion pumps with specially designed liquid-air cold traps and an oil rotary pump (250 l/min) as the fore pump ; baking, with Ni-Cr heater (300W) and by direct heating method (Transformer, 2KVA); monitoring system, available both for stoppage of electric current and suspension of water supply. Furthermore, a stainless steel gate valve was installed near the ion source (assembly) of the analyzer tube for the economy of evacuating time in the case of solid sample analysis. Results obtained with this system were described.

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A new type of pressure gauge has been developed by making use of the scintillation of atoms and molecules contained in a gas. The scintillation light is excited by electrons injected by an electron gun, so that the light intensity is proportional to the density of atoms and molecules. We examined the possibility of utilizing the above principle by observing the scintillation light excited by electrons of 1 KeV by means of a photomultiplier tube. The result indicated the linear relation between the pressure and the scintillation light intensity. The linearity broke down at 10^-4 mmHg, mainly because of the background light due to the scintillation light from a glass tube in which a vacuum was prepared. If an electron gun of good focus is employed, our method should be applicable in a vacuum range of 10^-3 to 10^-7 mmHg, the lower limit being due to the dark current of a photomultiplier. Methods for further improvement are proposed.

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