Abstract: An ionization source comprises a housing defining a space, a wire extending o the space, a temperature control connected to the wire and an alkali metal glass bead attached to the wire to be heated by the temperature control. An ion extraction plate with an orifice therein covers the space and is insulated from the housing by an insulating ring. The housing includes a port for drawing a vacuum from the space and for leaking molecules into the space which are to form quasi ions on the glass bead. A focusing plate may also be provided over the extraction plate with an aperture lying on an ion axis which also extends through the orifice for the focusing of the ion beam.