| 摘要 |
Disclosed is a structure aimed to reduce the frequency of replacement of an insulating spacer arranged between grids of an ion beam irradiation device. More specifically, disclosed is a so-called insulating spacer arranged in order to maintain insulation between the grids, the insulating spacer having an annular groove in a portion composed of an annular, substantially plane portion opposed to a grid and a cylindrical portion being raised from the central portion of the annular, substantially plane portion and abutting the grid, with the annular groove being perpendicular to the plane and separating the peripheral portion of the annular portion from the cylindrical portion.
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