| 摘要 |
PROBLEM TO BE SOLVED: To prolong life of an electron gun.SOLUTION: An electron gun cathode 104 has a columnar shape and emits electrons by being heated. An electron gun includes a holder 103 covering the bottom and side faces of the electron gun cathode, having electrical conductivity which holds the electron gun cathode, and comprising a material hardly reacting with the electron gun cathode in a heated state. The electron gun cathode 104 has a tip which is exposed and projects from the holder 103, and emits electrons from the tip toward the front with an application of an electric field to the tip. |
