| 摘要 |
In an inventive ion detector, a cylindrical conversion electrode and an electron multiplier are disposed on a vertical axis intersecting an incidence axis of an ion beam at a right angle. The space between the conversion electrode and the electron multiplier is enveloped by a shield electrode having a cylindrical body with its central axis on the vertical axis. By such a configuration, the electric field which is symmetrical with respect to the vertical axis is generated in the above space, so that secondary electrons or positive ions emitted from the conversion electrode as a result of a secondary emission, travel toward the electron multiplier, converging in proximity to the vertical axis. Thus, most of the secondary electrons or positive ions are led to the electron multiplier with its entrance placed on the vertical axis.
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