| 摘要 |
PURPOSE:To greatly reduce the number of times of minute discharge, by making the surface of a deceleration electrode convex in the face of a third electrode whose potential is kept between those of an acceleration electrode and the deceleration electrode, to suppress an electrical current loss resulting from the divergence of a beam. CONSTITUTION:The surface of a deceleration electrode 2' is made convex in the face of a third electrode 3 to make equipotential lines concave on the upside. As a result, an electric field is directed toward a center so that a force oriented toward the center acts to positive ions in a deceleration space between the electrodes 2', 3. For that reason, the divergence of an ion beam is diminished to decrease the quantity of the ion beam which collides against the electrode 3. This results in reducing the number of times of minute discharge.
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