An ion source made from a continuous dynode electron multiplier of the straight channel type and an ion reflector device is described. Its principle of operation is based on a continuous self-sustained ion and electron cascade in the multiplier channel. Operating characteristics and the analysis of the ions produced are presented. The intensity of the total ion current delivered (10−9 to 10−8 A) is enhanced by at least six orders of magnitude relatively to previously described similar devices. This source, as illustrated, may be used in gaseous mass spectrometry.