Preactivated highly efficient linear field ionization source

A new type of field ionization source is described. The emitter comprises carbonaceous dendrites grown along the edge of a 20-μm-thick tungsten foil by field ionization of pyridine at 1200 °C. The flow of the material to be ionized is directed to the ionization region by a second foil which defines a slit along the ionizing edge. This field ionization source, which provides a line-shaped image, has an ionization efficiency comparable to that of a well-activated multipoint source, and it does not undergo significant deactivation by negative ion bombardment.