| 摘要 |
PROBLEM TO BE SOLVED: To significantly prevent deterioration of aberration of emission electrons by forming at least one of electrodes by use of a high magnetic permeability material having a magnetic permeability of a specified value or more. SOLUTION: A suppressor 2 and extractor 3 which are electrodes, an outside magnetic pole 7b, and an inside magnetic pole 7c are formed of a high magnetic permeability material having a magnetic permeability (at 0 deg.C) of 10 or more such as electromagnetic soft iron, pure iron, silicon steel, permalloy or the like. A magnetic pole unit 7 arranged in the rear of the extractor 3 is formed of a permanent magnet 7a, the outside magnetic pole 7b and the inside magnetic pole 7c. The extractor 3 is integrally formed with the outside magnetic pole 7b through an insulator 9a, and the suppressor 2 is integrally formed with the inside magnetic pole 7c through an insulator 9b. Since the flow of magnetic flux is in a narrow gap between the suppressor 2 and the extractor 3, and this position is extremely close to Z-axis, a steep magnetic field having a high peak can be applied to the vicinity of an emitter 1.
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