| 摘要 |
An electronic gun is provided to keep constantly a replacement cycle of a cathode tip by controlling easily the distance between the cathode tip and an anode using a piezoelectric motor installed at the cathode tip. An electronic gun includes a cathode tip(51) for emitting electrons, a piezoelectric motor, a Wehnelt cylinder, a laser beam emitting unit, a light receiving sensor, and an anode. The piezoelectric motor(55) is installed at the cathode tip by using a heater block. The piezoelectric motor is capable of moving precisely the cathode tip up and down. The Wehnelt cylinder(63) is used for holding the cathode tip. The Wehnelt cylinder includes a hole capable of passing a laser beam at both lower sides and an emitting hole for emitting electronics from the cathode tip at a lower portion. The laser beam emitting unit(65) is installed at one side of the Wehnelt cylinder in order to transmit the laser beam through the hole. The light receiving sensor(67) is installed at the other side of the Wehnelt cylinder in order to receive the laser beam through the hole. The anode(69) is installed under the Wehnelt cylinder.
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