| 摘要 |
PURPOSE:To reduce the aberration thus to reduce the image magnification, by arranging the focusing electric field with substantially no gap following to the diverging electric field then producing the focusing point of an ion beam in the proximity of the exit of the focusing electric field through said focusing electric field. CONSTITUTION:The ion beam from an ion source 1 passed through a main slit 2 will pass through a diverging troidal electric field E1 formed betwen the electrodes 3, 4 and a converging troidal electric field E2 formed between the electrodes 5, 6 and temporarily focused at point P. The ion beam passed through an intermediate slit 7 positioned at point P is combined with the electric fields E1, E2 and provided to the fan-shaped uniform magnetic field 8 arranged to satisfy the double focusing requirement, then focused by said magnetic field 8 to the collector slit 9. A tetra- pole lens 10 is arranged between the said slit 7 and the magnetic field 8. |
