| 摘要 |
PURPOSE: To always monitor both of beam current and high voltage by establishing a threshold curve for the combination of two parameters of the beam current and high voltage, and when the combination of the beam current and high voltage exceeds a threshold, generating a trigger signal. CONSTITUTION: When high voltage is maintained at a fixed level and a beam current is continuously increased, voltage appearing on the base of a transistor(TR) 26 is dropped lower than the emitter-base threshold voltage of the TR 26 and the TR 26 is turned on, a current is allowed to flow from a rectifier circuit 32 into ground through a resistor 30, the TR 26, a diode 42, and a resistor 44, a voltage drop is generated between both the terminals of the resistor 44 and a trigger signal to a trigger response device 48 is generated to interrupt the current. When a beam current is maintained at a fixed value and high voltage is continuously boosted, voltage appearing on the emitter of the TR 26 is boosted over the voltage appearing on the base of the TR 26, the TR 26 is conducted, a current is allowed to flow into the resistor 44, and a trigger signal is applied to the device 48. |
