An ion source comprising an electrode consisting of at least one body made of a material such as to be perfectly wetted by a liquid material ions of which are to be emitted by the source and not corrodible by that material, and having a termination the radius of curvature of which is such that a jet of the liquid material will form and be anchored to the termination of the electrode under the influence of an electric field, means for applying the ionizing electric field and a reservoir for the material ions of which are to be emitted by the source.

An ion beam generating apparatus is used together with a vacuum chamber. The ion beam generating apparatus has an anode assembly arranged inside the vacuum chamber, a gas supply mechanism for supplying a gas into the vicinity of the anode assembly, a temperature control mechanism for controlling a temperature of an apex of the anode assembly, and a cooling mechanism for cooling at least part of the anode assembly.

An ion source having a sintered metal head for ionizing various substances is disclosed. This ion source comprises a container made of a material which has a higher fusing point than that of the substance which is to be ionized, and a tip formed of a molded sintered metal of a higher fusing point than that of the substance which is to be ionized. The head is formed into a nearly conical shape and has a porosity capable of allowing the substance which is to be ionized to infiltrate therethrough in the molten state and the tip of the head is positioned at the opening of one end of the container for the ionizable material and arranged in such a manner that it protrudes beyond the end of the container.