Abstract: An electron gun includes an electron emission cathode, a control electrode, and an extractor and the electron emission cathode is made of rare earth hexaboride. A tip of the electron emission cathode is located between the control electrode and the extractor, and the electron emission surface of the electron emission cathode is spherical or flat.

Abstract: An electron gun comprising an electron emission cathode, a control electrode and an extractor wherein the electron emission cathode is mode of rare earth hexaboride and a tip of the electron emission cathode is located between the control electrode and the extractor.

Abstract: A liquid metal ion source comprises a reservoir storing a metal to be ionized and a needle electrode to which the metal is fed from the reservoir wherein the size of small pits formed in at least a cone surface of the needle electrode is 0.1 &mgr;m-1.5 &mgr;m and the small pits exist in the cone surface of the needle electrode in a density of 5×104 number/mm2-5×106 number/mm2 the small pits being formed by chemically etching.

Abstract: A gallium ion source including a needle electrode, a reservoir for storing gallium, and a wire heater for heating the needle electrode and the reservoir. The needle electrode, the reservoir and the gallium stored in the reservoir have total heat capacity of not less than 0.015 J/K and not higher than 0.1 J/K. The needle electrode and reservoir of the gallium ion source may have a total heat capacity of 0.015 J/K to 0.1K and the initial amount of gallium is 0.004-0.10 g, The wire heater may have a diameter of 0.10-0.20 mm and a length of 8-30 mm, and may be in a V shape with a bend angle of 40°-90°.

Abstract: A thermal field emission cathode comprising a tungsten single crystal having an axis direction of <100> and a coating layer of zirconium and oxygen formed thereon, wherein a source for supplying zirconium and oxygen contains an element capable of forming cubic or tetragonal zirconium oxide at an operation temperature of the thermal field emission cathode.

Abstract: A method of making a needle electrode is such that a neck portion is formed in a thin wire made of a tungsten single crystal and the thin wire is cut at the neck portion by feeding an electric current in electrolyte.

Abstract: A thermal field emission electron gun has a thermal field emission cathode and a suppressor electrode wherein the thermal field emission cathode comprises a single crystal tungsten needle of an axis direction of <100> and a coating layer composed of zirconium and oxygen, and the suppressor electrode is composed of either titanium or an alloy including titanium as the major component, of which hydrogen content is 60 ppm or less. Electron beams can be stably obtained with good reproducibility in a short time.

Abstract: A thermal field emission cathode comprises a needle-like electrode of single crystal tungsten having an axis direction of <100> provided with a coating layer of zirconium and oxygen; a heater for heating the needle-like electrode; a suppressor electrode; and a supply source for supplying zirconium and oxygen having zirconium of not less than 3.0.times.10.sup.-6 g and not more than 10.times.10.sup.-6 g by weight to the coating layer disposed on the needle-like electrode in a range between a point apart from a junction of the needle-like electrode and the heater by 200 .mu.m in a direction of a distal end of the needle-like electrode and a plane including an outer surface of the suppressor electrode.