| 摘要 |
PURPOSE:To make possible to increase the current density of an ion beam, by connecting a heat radiation shield which encloses the ion beam generation part to a refrigerator and also, making the shield have a specified wall thickness so that it can cool the vicinity of the beam generation part. CONSTITUTION:Through a nozzle 2 Helium gas or the like is introduced to a space airtightly sealed by a heat radiation shield 4, and by applying a high voltage between a needle-shaped electrode mounted on a refrigerator 12 through an insulation sapphire 13 and a drawing electrode 3, an ion beam is drawn out. Thus an ion gun for a focusing ion beam device is constituted. In this case, the heat radiation shield 4 is formed with copper of about 5mm, and its top part is closely attached to the refrigerator 12 ranging a wide avea. Also, the relation between a radius R of the shield 4 and a radius of curvature r of a needle electrode holder 14 is made to be R > 10r. Thus, cooling effect of the shield 4 is increased and also, unnecessary discharge is avoided so that the ion current density can be increased.
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