Saturday, July 15, 2017

SBIR-STTR-Far-Tech-DOE Robust S-Band thermionic RF gun with improved back-bombardment suppression

10350 Science Center Drive, Ste 150, San Diego, CA, 92121-1136

 David Newsham
 (858) 455-6655

Thermionic electron sources operating a microwave frequencies with longer lifetimes and increased performance will improve the reliability of synchrotron light sources and a new generation of high power terahertz light sources. Increasing the reliability of the electrons sources will improve the stability of operation for users. The robust thermionic electron source uses a short initial cell, followed by a cavity that is electrically uncoupled from the initial cell. The initial short gap delays the launch phase at which back-bombardment of the electrons onto the cathode will occur. This effectively decreases the beam power that will heat the cathode and increased the possible pulse width. The second cavity is uncoupled to the first cavity and is driven independently to maximize beam capture. In Phase I, the feasibility of producing the novel gun design will be determined through RF and beam dynamics simulation. The effectiveness of the short first cell followed by an independently driven cavity will be verified. The ability to cancel the coupling between the two cells will be confirmed and a design of the whole cavity structure will be developed. The cathode mounting system will be designed. Thermionic electron sources operating at microwave frequencies are current limited by electrons that reflect back from the radio frequency fields and heat the cathode. A novel cavity design is being investigated that will decrease the number of reflected electrons and improve the efficiency of the overall electron source. Commercial Applications and Other Benefits: This cavity will be an improvement over existing thermionic guns, allowing for operation at increased duty factor do to the reduction of the electron back-bombardment on the cathode. It has potential uses in synchrotron light sources and high power terahertz sources.

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