The Static Operation Mass Spectrometer

A mass spectrometer has been designed for the studies on the adsorption of CO, CO 2 and O 2 in a closed system. The spectrometer is a 60° sector type of 10 cm in radius, and made of Pyrex glass. The electrodes are made of gold and silver, and a tin-oxide coating is adopted as the conductive coating. The field emission cathode operated at room temperature is used as the electron emitter of the ion source in stead of a glowing tungsten filament. The above construction is based on the results of the experiments on the activity of O 2 on semi-clean surfaces of the electrode materials. The spectrometer can be operated statically in ultrahigh vacuum of 6 × 10 -10 Torr. The static operations for Ar, H 2 , N 2 and CH 4 can be made in the best condition, and those for n –C 4 H 10 , CO, CO 2 and O 2 , which could not be analyzed statically using a spectrometer with a glowing filament, can be also made in good condition. The detectabilities for the above gases are about 5 × 10 -8 cc N.T.P., which are satisfactory for adsorption experiments in a closed system.