| 摘要 |
PROBLEM TO BE SOLVED: To optimize placement positions of parts surrounding an electrode and to improve focus characteristics of an electron beam. SOLUTION: In the circumference of each electrode, beaded glasses 9a and 9b are disposed on the positions opposed to each other on a Y axis. In the circumference of each electrode, an internal divided resistor 8 is disposed, for example, on an X axis orthogonal to the Y axis. A G4 lead 11 is disposed, for example, on the position approximately in the middle of the beaded glass 9a and the internal divided resistor 8. In the circumference of each electrode, a high-voltage supply lead wire 12 is placed on the position so as to allow an electric field in the electrode formed by each electrode to be distributed with proper potential. For example, the high-voltage supply lead wire 12 is opposedly disposed on the line connecting a center axis O of each electrode to the G4 lead 11 relative to the G4 lead 11. The mounting position of the high-voltage supply lead wire 12 is not completely symmetric to the G4 lead 11 and can be adjusted ranging an angle±α.
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