| 摘要 |
PURPOSE:To obtain sufficient intensity of magnetization and improve correction accuracy by composing a magnetic field for correcting an electron beam orbit while combining all the local magnetic fields with various sizes of their sectional areas in the circumferential direction surrounding a central electron beam. CONSTITUTION:The pattern PN of a magnetic field is composed of a magnetic field generating means, for instance, an anisotropic magnet 12 while being composed of combination of the magnetic field part for main correction PN1 having a big magnetic field sectional area in the circumferential direction and the small magnetic field part for minute correction PN2, whereby said magnetic field parts PN1 and PN2 have a positional relation to be alternately arranged each other in the circumferential direction. The N1 pole and the S1 pole in said PN1 having a big magnetic field sectional area are to be, for instance 2.5 times the plate thickness of an anisotropic magnet material to be used, while the N-pole and the S- pole in the small PN2 are to be 0.6 times etc. said plate thickness. Thereby, it is easy to make correction even when a correction amount is big, while correction accuracy can also be improved. |
