PURPOSE: To permit the radiation of heated negative ions by coating sample liquid through a capillary tube on the surface of a metallic cylinder which is equipped with a surface-ionized type cesium ion source and filled with ionized material for red heat, forming a porous face.

CONSTITUTION: A high-frequency heating heater 5 is provided inside a cesium ion source with a surface ionized system to make tantalium(Ta), thin material for a metallic cylinder 4 which is filled with ionized material, interchangeable with other platinum(Pt), tungsten(W) and molydbenum(Mo) for mounting. Then, an ion rediator 7, mixture of a sample with metallic powder, is directly injected into a metallic cylinder 4 or directly coated on the surface of the cylinder 4 through a capillary tube 8 to remove solvent by a high-frequency heating heater 5, forming a sintered porous face. Therefore, it acts in the same way as a cesium(Cs) ion source because of limited occurrence of ions (radiated face) in a specific small space. It is thus possible to produce heated negative ions easily.