Secondary Emission Electron Gun Using External Primaries

A method for generating an electron beam comprising the steps of:

• providing a primary beam comprising primary accelerated electrons, the primary beam being substantially directed at a secondary emitter;
• emitting secondary electrons from the secondary emitter in response to contact with the primary accelerated electrons;
• and
• generating the electron beam by accelerating the secondary electrons in an accelerating region, a cathode providing the primary beam being disposed external to the accelerating region.

A method for generating a high-brightness high-current electron beam comprising the steps of:

• inserting an encapsulated secondary emission enhanced cathode device into a radio frequency accelerating cavity, the encapsulated secondary emission cathode device comprising a high quantum efficiency cathode and a non-contaminating secondary emitter;
• adapting the high quantum efficiency cathode to emit primary electrons, the non-contaminating secondary emitter emitting secondary electrons in response to the primary electrons;
• and
• providing an electric field to accelerate the primary electrons to the input surface of the secondary emitter and to accelerate the secondary electrons through the secondary emitter, the secondary electrons emitted from the encapsulated secondary emission enhanced cathode device being further accelerated by the electric field to generate the high-brightness high-current electron beam.

A lasertron for providing radio frequency power comprising:

• a photocathode, the photocathode emitting primary electrons in response to a laser beam;
• a secondary emitter, the secondary emitter comprising:
• a non-contaminating negative-electron-affinity material;
• an input surface, the input surface receiving the primary electrons, the input surface comprising a substantially uniform electrically conductive layer, the substantially uniform electrically conductive layer providing a replenishing current to the secondary emitter, the electrically conductive layer being substantially transparent to the primary electrons;
• and
• an emitting surface, the emitting surface comprising a non-contaminating enhanced negative-electron-affinity surface;
• an anode, the secondary electrons being accelerated from the secondary emitter to the anode by a direct current electric field applied between the secondary emitter and the anode;
• and
• an extraction cavity, the extraction cavity receiving the secondary electrons and providing radio frequency power output.