On A. C. Amplification of Ion Currents for Mass Spectrometer

A simple a. c. amplifying system for a mass spectrometer is described. Thermally modulated ion currents emitted from triple-filaments heated by 50 c/s a. c. power were amplified and mass spectrum of K was recorded. In the present system, the a. c. component of the ion currents lags in phase about 60° from the supply voltage of the filaments, and it amounted to about 10% of the d. c. component. The results predict the merits of an a, c. amplifier over a colwentional direct-coupled d. c. amplifier in its slmplicity and sensitivity when the ion currents are modulated more deeply.