1977 Volume 25 Issue 3 Pages 211-215
A High efficiency ion source which produces low energy ions(100∼500eV)is described. In order to prevent the decrease of ion intensity due to low accelerating potential, negative high voltage is applied to the main slit. Ions are first accelerated to several thousand volts and then decelerated to several hundred volts af ter passing through the main slit. Almost the same ion intensity was obtained compared to ordinary ion source with high accelerating potential. The decrease of resolving power due to low accelerating potential was negligible when the ion source was attached to a double focusing mass spectrometer of second order. This type of ion source is useful for mass analyses of very heavy organic compounds, because very strong magnetic field is not required.