| 摘要 |
<p>PURPOSE:To make a microwave tube compact in size and have high precision and improve its reliability and efficiency, by dividing an emitter electrode into a plurality of parts and making it possible to switch two current modes at high current and low current by altering the voltage applied. CONSTITUTION:While being set to intersect each other right and left and to cover a circular electron emission region, a first emitter electrode 5 and a second emitter electrode 6 of metal thin films are formed on an insulating substrate 1. When a switch 7 is set at B position, a cold cathode is turned in the high current mode and an electric field is applied to the tips of all of the emitters 4 and electrons are emitted from the whole surface of the cathode, that is, the emitters 4 in the whole surface of the circular electron emission region. When the switch 7 is set at A position, the cold cathode is turned in low current mode and the electrode 6 is kept at the same potential as that of gate electrodes 3, so that electrons are not emitted from the emitters 4 formed on the electrode 6 and electrons are emitted only from the emitters 4 formed on the electrode 5. Consequently, axially symmetric and excellent emission current distribution can be obtained.</p> |
