A Sheet Beam Electron Gun Based on Carbon Nanotube Cold Cathode

Cold cathode is a compelling candidate for compact and high-frequency vacuum electronic devices (VEDs) due to its superior electron emission characteristics, and sheet electron beam is more suitable for planar high-frequency VEDs. To combine cold cathode with sheet electron beam to manufacture a high-performance electron gun is a promising strategy. This article presents the design and fabrication of a sheet beam electron gun based on carbon nanotube (CNT) cold cathode and carries out the experiments to validate its performance. The designed electron gun with a sheet-shaped CNT cathode and an asymmetric focusing electrode can effectively generate and transmit a sheet electron beam. A sheet-shaped CNT cathode was fabricated using thermal chemical vapor deposition (CVD) for CNT growth and laser etching technique for sheet CNT pattern. An asymmetric focusing electrode utilized in the electron gun can effectively eliminate edge emission effect and achieve uniform sheet electron beam focusing. In the experiments, the sheet electron beam with dimensions of $2.86\times0.41$ mm is uniform and maintains the desired shape generated by the CNT cold cathode. The electron gun can operate in the pulse mode at a maximum beam current of 1.92 mA, corresponding to a beam current density of 0.23 A/cm2. This work establishes a solid foundation for further research on sheet beam generation by using CNT cold cathodes and expands their applicability in microwave VEDs.