| 摘要 |
[Objection of the invention]An ion beam generator, a thermal distortion in a grid assembly is reduced. [Structure to solve the objection]Thermal expansion coefficients αP, αM and αG, for a sidewall (1A) of a discharge chamber, mounting platform (40) and extraction grid electrode assembly (20) are selected to have a relation: αP>αM≧αG. For example, the material of discharge chamber sidewall is stainless steel o aluminum, the material of grids is Mo, W or C and the material of platform is Ti or Mo.
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