| 摘要 |
PURPOSE:To keep the shape or an emitter tip constant and obtain a stable high-brightness ion beam by gradually increasing the cooling temperature of a refrigerator and discharging the adsorption gas from a cooling face so as not to increase the pressure of an ion source. CONSTITUTION:The voltage of a power supply 23 is adjusted to control the heating current of a heater 22. This power supply 23 is connected to a control system 20 monitoring the degree of vacuum of a vacuum meter 24. According to this constitution, after the operation is stopped, a refrigerator 21 is continuously operated as it is, and the vacuum exhaust is also continued. The degree of vacuum of an ion source 20 is measured, and the pressure (degree of vacuum) is controlled not to exceed the preset value. Accordingly, the shape of an emitter tip is kept constant, and a stable high-brightness ion beam can be obtained.
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