EXPERIMENTAL INVESTIGATION OF THE BENNETT TYPE RADIO-FREQUENCY SPECTROMETER,

Authors conducted experiments to study the static characteristics of a Bennett radio-frequency RF mass spectrometer. Bennett RF mass spectrometer is used to determine individual constituent contents in gaseous mixtures. The gaseous mixture is ionized by electron emission. The vacuum system which is capable of creating a vacuum of 0.000001 mm Gh for the mass spectrometer consists of a mechanical pump, an oil diffusion pump, a cryogenic arrester, a gallium-sealed ultrahigh vacuum switch, a cold-cathode titanium pump, a JIM-2 LM-2 ionization vacuum gage, a B-A ionization gage, and a RF mass spectrometer tube with one end sealed. The electronic circuit in the mass spectrometer consists of an ion source, a low ionization current measuring circuit, an ion-accelerating sweep power supply unit, a high-frequency power supply unit, and a regulated power supply unit. The sawtooth generator in the ion-accelerating sweep power supply unit has an output sweep voltage of 50-250 v and a sweep frequency of 7-12 cps. Charging and discharging of the sawtooth generator is controlled by a thyration. The high-frequency power supply unit is a fixed frequency oscillator having an operating frequency of 5 and 2 mc. A mass spectrogram of the residual gases left behind by the cold-cathode titanium pump can also be produced. Observations showed that secondary peaks appear on the oscillogram at an extremely high bias voltage or an extremely low damping voltage. A low-noise a.c. amplifier or a d.c. amplifier is used to measure the spectral lines of gases. The measuring accuracy of the oscilloscope can be improved if used in conjunction with a d.c. amplifier. Author