A Carbon-Nanotube Cold-Cathode Reflex Klystron Oscillator: Fabrication @ X-Band and Returning Electron Beam Realization

Abstract

This paper presents the design and fabrication of a reflex klystron oscillator based on a carbon nanotube (CNT) cold-cathode. An X-band klystron oscillator structure is assembled with a CNT cold-cathode electron gun with an electrostatic focusing, a re-entrant cavity as anode, and a repeller. The electron gun adopts a convex CNT film emitter as the cathode. A re-entrant cavity resonating at 8.376 GHz is fabricated. The study mainly focuses on the returning electron beam in the klystron oscillator structure. The experimental results of variations of the anode current and returning electron beam amplitude with repeller voltage are presented. It is demonstrated that a higher extracting voltage of the cold-cathode has an important influence on the returning electron beam. To decelerate electron velocity from the extracting voltage, increasing negative focusing voltage and focusing electrode height in the electron gun can improve the returning electron beam characteristics.

Boosting the electron beam transmittance of field emission cathode using a self-charging gate

“…Moreover, the E-beam transmittance and long-term stability tests (310 h) of the cathode engineering prototype upon the external stimuli were also conducted to verify the stability and reliability of the charging of SiN x -gate, and test results indicate that the cathode can maintain current stability and high E-beam transmittance even under/after external stimulation (Supplementary Figs. [19][20][21][22][23][24][25][26][27][28][29][30][31]18). Therefore, the asprepared cathode with long-term stability and high transmittance under wide-range current and external stimuli is well-suited for the in-space applications mentioned above.…”

“…The most straightforward approach is to reduce the gate aperture ratio, whereas the thickness and width of the gate cannot be too small in order to meet the structural robustness and material processing requirements 26 . Alternative approaches, by placing external forces such as electrostatic and magnetic forces on the E-beam, are considered to achieve the E-beam focusing for higher transmittance 27,28 . Han et al developed a curve-shaped elliptical focusing lens above the gate, which achieved a high E-beam transmittance of 95.2%, showing a path for the high-performance X-ray tube 29 .…”

Boosting the Electron Beam Transmittance of Field Emission Cathode Using a Self-Charging Gate

“…[47][48][49] Alternative approaches, by placing external forces such as electrostatic and magnetic forces on the E-beam, are considered to achieve the E-beam focusing for higher transmittance. [50][51][52][53] J. S. Han et al developed a curve-shape elliptical focusing lens above the gate, which achieved a high E-beam transmittance of 95.2%, showing new path for the highperformance X-ray tube. 54 J. Zhang et al demonstrated the effectiveness of introducing external magnetic field to enhance the performance of the gate-type cathodes.…”