左边的阴极被灯丝加热到高温，同时电子从阴极表面蒸发出来。
The cathode at the left is raised to a high temperature by the heater, and electrons evaporate from its surface.
中和阴极灯丝电源的正极接地，使得整个中和阴极灯丝处于负电位；
Anode of power supply for neutralization cathode filament is connected to ground, so that filament is at negative potential.
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