| 摘要 |
PURPOSE:To correct a gap between voltage and current axes by arranging an auxiliary yoke made of a ferromagnetic body that is axisymmetrical to the outside of a yoke inner cylinder and has length in the axial direction of the yoke inner cylinder. CONSTITUTION:In a cylindrical body that is provided with a magnetic pole piece 5 at a magnetic pole gap section 3 and length in the direction of a lens axis O between a yoke inner cylinder 1 and an excitation coil 4, a number of rod bodies are integrated axisymmetrically and an auxiliary yoke 6 made of a ferromagnetic material can be moved within a plane perpendicular to a lens axis (yoke inner cylinder axis). The tips of several adjusting screws 7a, 7b... are made to touch this auxiliary yoke 6. The shift size and direction of the auxiliary yoke for the lens axis O can freely be varied by properly adjusting these adjusting screws. As a result, a gap between voltage and current axes can easily be corrected and the deterioration of the resolution caused by the shift of both axes can be prevented. |
