| 摘要 |
PROBLEM TO BE SOLVED: To make a quadrupole lens operable under the optimum condition suitable to an individual electron gun, by superimposing control voltage from a set side control circuit part, on a dynamic power source part to adjust first focusing voltage. SOLUTION: First focusing voltage Ea is made to set optionary to optimize an electric potential differenceΔv, between second and first focusing voltage Eb and Ea, despite fluctuation in material for constituting an electron gun 1 and in assembling accuracy, exists. A voltage waveform, specifically clamped, is obtained by superimposing the focusing voltage Ea on the control voltage dynamic power source part Ed of a control circuit part Ec supplied from a set side, to decide the focusing voltage Ea, also to automatically decide the electric potential differenceΔv, between the focusing voltage Eb and Ea. An adequate electric potential differenceΔv can be obtained, by thus clamping the voltage waveform by control voltage from the control circuit part Ec adequate to the individual electron gun 1.
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