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Brazed carbon fiber fabric field emission cathode
Brad W Hoff1, Sterling Beeson1, David Simon1
1Air Force Research Laboratory, Directed Energy Directorate, Kirtland AFB, New Mexico 87117, USA.
The Review of Scientific Instruments
|July 3, 2020
Summary
New field emission cathodes use carbon fiber fabrics brazed to metal, avoiding epoxy. These high-temperature-stable cathodes achieve high current densities, matching previous epoxy-bonded designs.
Area of Science:
- Materials Science
- Physics
- Engineering
Background:
- Field emission cathodes are crucial for various applications.
- Traditional cathodes often rely on epoxy bonding, limiting thermal stability.
- Developing robust, high-performance field emitters is an ongoing challenge.
Purpose of the Study:
- To fabricate and test novel field emission cathodes using direct brazing.
- To evaluate the performance of brazed carbon fiber cathodes at high voltages.
- To assess the thermal stability advantages over epoxy-bonded designs.
Main Methods:
- Commercially available carbon fiber fabrics were directly brazed to metal substrates.
- Fabricated cathodes were tested under vacuum conditions.
- Current emission densities were measured at mildly relativistic voltages (200 kV-300 kV).
Main Results:
- The brazed cathodes eliminated the need for epoxy bonds.
- Cathodes demonstrated high-temperature baking capabilities, limited only by braze re-melt temperature.
- Average current emission densities reached hundreds of A/cm².
Conclusions:
- Direct brazing offers a viable, high-temperature-stable alternative to epoxy for fabricating field emission cathodes.
- The performance of brazed cathodes is comparable to epoxy-bonded designs.
- This fabrication method holds promise for advanced electron emission applications.
