Electron emission device and reflex klystron with the same

A reflex klystron, comprising:

• a first substrate and a second substrate spaced from each other, wherein the first substrate and the second substrate are coupled together to form a resonant cavity;
• a lens, wherein the lens is located on an end of the resonant cavity and configured as an output portion;
• an electron emission device, wherein the electron emission device is configured to emit a plurality of electrons into the resonant cavity, the plurality of electrons are oscillated in the resonance cavity, and the electron emission device comprises:
• an electron reflective structure on the second substrate, wherein the electron reflective structure comprises a reflective electrode and a second grid spaced from each other;
• an electron emission structure on the first substrate, wherein the electron emission structure comprises a cathode, an electron extraction electrode, an electron emitter structure, and a first grid, the electron extraction electrode defines a through hole surrounded by a sidewall, the electron emitter structure comprises a conductor and a plurality of electron emitters on the conductor and extending toward the through hole, each of the plurality of electron emitters comprises an electron emission terminal, a distance between the electron emission terminal and the sidewall is constant, and a pressure in the electron emission device is smaller than or equal to 100 Pascal.

An electron emission device, comprising:

• an anode;
• a cathode spaced from the anode;
• an electron emitter structure electrically connected to the cathode;
• an electron extraction electrode insulated from the cathode via an insulating layer, wherein the electron extraction electrode defines a through hole surrounded by a sidewall, and the electron emitter structure faces to the sidewall;
• wherein the electron emitter structure comprises a plurality of electron emitters extending toward the sidewall, each of the plurality of electron emitters comprises an electron emission terminal, a first distance between the electron emission terminal of each of the plurality of electron emitters and the sidewall is constant, a second distance between the electron emission terminal and the anode is greater than or equal to 10 micrometers and smaller than or equal to 200 micrometers, and a pressure in the electron emission device is smaller than or equal to 100 Pascal.