| 摘要 |
PURPOSE:To obtain a high resolution even at high intensity by giving a specific relation between aperture diameters and electrode separations of G2, G3, G4 electrodes and applying a low potential to the G4 electrode so as to generate a strong focus lens with the G2, G3 electrodes and a strong divergent lens with the G3, G4 electrodes. CONSTITUTION:The G2 electrode 3, G3 electrode 22, G4 electrode 23 and G5 electrode 24 are provided from the G1 electrode 2 side as a control electrode to the G6 electrode 21 side as a final acceleration electrode in sequence. Equations D2<=D3<=2D2, D3<=D4<= 2D3, 0.5D2<=g23<=1.5D2, 0.2D3<=g34<=1.5D3 are satisfied, where D2, D3, D4 are aperture diameters of the G2, G3, G4 electrodes respectively, g23 is a separation between the G2 electrode and G3 electrode, g34 is a separation between the G3 electrode and G4 electrode. In addition, a potential lower than that of the G3, G5 electrodes is applied to the G4 electrode so that the axial potential distribution becomes the maximum value at the G3 electrode area then is gradually decreased at the G4 electrode area to the minimum value and is continuously increased at the area from the G4 electrode to the G6 electrode, a strong focus lens is generated with the G2 electrode and G3 electrode, and a strong convergent lens is generated with the G3 electrode and G4 electrode. |
