| 摘要 |
PROBLEM TO BE SOLVED: To provide an electron gun causing no flow of great emission current in starting. SOLUTION: A heat quantity fed to a cathode is controlled to be constant. By advance measurement, the heat quantity is decided so that a temperature of the cathode is slightly lower than a temperature at the start of emission in the cathode when an equilibrium state is established by continuous supply of the heat quantity. When a temperature around the cathode reaches an equilibrium state, a controller lets current larger than that flowing through a filament so far flow in the filament for heating the cathode. At the start of the emission current flow, feedback control operating current to be let flow through the filament is started so that the emission current is kept constant. In this way, the heat quantity fed to the cathode 1 is increased slightly, and the emission current slightly overshoots a target value and then converges at a target value, and the overshoot quantity is greatly reduced in comparison with that by a conventional control method. COPYRIGHT: (C)2007,JPO&INPIT
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