Mono-kinetic ion source for a single focusing mass spectrograph.

The design, construction and performance of a hot-cathode oscillating electron mono-kinetic source of positive ions are described. The source is designed for a single-focusing mass spectrograph for the mass-identification of radioactive positive ions. Electrons from a hot cathode focused by a weak magnetic field (400 gausses), oscillate in a reflection type electric field to generate positive ions in a metallic vapour issuing from an internal furnace. Positive ions are partially focused by the electron space charge. The source is mono-kinetic within 3 volts. Positive ion currents of 3 x 10-9 A of Cadmium were obtained at moderate furnace temperatures for electron space currents of 15 ul