Available Technology

BSA 12-27: Diamond Amplified Photocathode for the Generation of High-Current High Brightness Electron Beams

A vacuum encapsulated, hermetically sealed diamond amplified photocathode capsule for generating a high-intensity electron beam and a method for making the same. In an electron gun device, a diamond amplified photocathode can perform multiple functions: 1) It amplifies the primary current from a conventional photocathode with amplification factors exceeding 200, thereby reducing the demands on the primary cathode and the laser; and 2) It also acts as a window that isolates the cathode from the RF cavity, thereby shielding them from contaminating each other.
Patent Abstract: 
This invention comprises a vacuum encapsulated, hermetically sealed high temperature cathode capsule for generating an electron beam of secondary electrons. The capsule generally includes a cathode element having a primary emission surface adapted to emit primary electrons, an annular insulating spacer, a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element, a first high temperature solder weld disposed between the diamond element and the annular insulating spacer and a second high temperature solder weld disposed between the annular insulating spacer and the cathode element. The present cathode capsule of the present invention is formed by a high-temperature weld process under vacuum such that the first solder weld forms a hermetical seal between the diamond window element and the annular insulating spacer and the second solder weld forms a hermetical seal between the annular spacer and the cathode element whereby a vacuum encapsulated chamber is formed within the capsule. Preferably, the first and second solder welds are made with a material comprising 96.8 gold (Au)/3.2 silicon (Si). Also, the cathode element, the diamond window element and the annular insulating spacer preferably have interface surfaces coated with a metallic wetting material, wherein the metallic wetting material is in contact with one of the first and second solder welds to promote atomic adhesion therebetween. With 96.8Au/3.2Si solder blanks, use of a gold (Au) wetting material is preferred.
Benefits 
In an electron gun device, a diamond amplified photocathode can perform multiple functions: 1) It amplifies the primary current from a conventional photocathode with amplification factors exceeding 200, thereby reducing the demands on the primary cathode and the laser; and 2) It also acts as a window that isolates the cathode from the RF cavity, thereby shielding them from contaminating each other.
applications 
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