| 摘要 |
PROBLEM TO BE SOLVED: To easily change the shape of a beam. SOLUTION: An ion beam emitting grid in an ion gun 14 is composed of two grids (a screen grid and an accelerating grid) 21, 22 for which grid holes 24 are formed throughout their surfaces, a doughnut plate-like ion beam molded- plate 23 incorporated in between the two grids 21, 22 and the ion gun 14. The shape of the beam is determined by the shape of a molded hole 25, so that the shape of the beam can be changed by replacing the ion beam molded-plate 23, while the grids 21, 22 are left as they are.
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