| 摘要 |
PURPOSE:To realize stable mass convergence over wide mass range by arranging a multi-pole lens or lenses in front and/or rear of the magnetic field while varying the applying voltage with correspondence to the strength of the magnetic field thus regulating the substantial focus distance. CONSTITUTION:The ion beam from an ion source is converged through an electrostatic lens onto an ion source slit 11 then diverged horizontally through four-pole lenses 2, 3 and enters into the magnetic field 5 while converged in vertical direction. In is diverged with correspondence to the magnitude of mass in the magnetic field to pass only such ions as having specific mass through four-pole lenses 6, 7 and reach to an ion collector 8. In order to correct variation of focus point due to mass thus to focus continuously to fixed position, the strength of magnetic field is monitored through a Hole element 9 thus to provide a signal proportional to the strength of magnetic field to a function generator 12. The output from the function generator is proportional to the potential of four-pole lenses 3, 6 providing the optimal focus condition for any strength of magnetic field thus to control the four-pole lens control power source 13. |
