Abstract: An electron emission device for attracting electrons emitted from an electron emission element to an anode, includes a current detector for detecting a flow-in current to said electron emission element and a flow-out current from the electron emission element. The difference between the flow-in current and the flow-out current is calculated and the voltage applied to the electron emission element is adjusted in accordance with the difference between the flow-in current and the flow-out cuttent.

Abstract: An alignment device including an electron gun for emitting an electron beam, a deflecting electrode for scanningly deflecting the electron beam emitted from the electron gun, a holder for holding an object in a plane of scan, a reference mark with which the object is to be aligned, and a detector for detecting electron beams emerging from the reference mark and the object, which are irradiated by the scanning electron beam, to detect the position of each of the reference mark and the object. On the basis of result of detection by the detector, the object is displaced by a drive source, whereby it is precisely aligned with the reference mark.

Abstract: A reservoir containing a material to be ionized has in its bottom a capillary extending outwardly in symmetrical with the optical axis of an ion source, and has a needle extending coaxially through said capillary in said reservoir so that the apex end of the needle projects slightly beyond the exterior surface of the reservoir. Intensive electric field at the apex end of the needle is formed by an extracting electrode disposed in facing the needle. An electric current is supplied through conductive wires or filaments supporting the reservoir for heating the reservoir. As a result, the liquid material to be ionized in the reservoir seeps smoothly through the capillary of the reservoir toward the apex end of the needle for field evaporation and ionization.