A vacuum sealed high emission current and transmission efficiency carbon nanotube triode

Abstract

A vacuum sealed carbon nanotubes (CNTs) triode with a concave and spoke-shaped Mo grid is presented. Due to the high aperture ratio of the grid, the emission current could be modulated at a relatively high electric field. Totally 75mA emission current has been obtained from the CNTs cathode with the average applied field by the grid shifting from 8 to 13 V/μm. Whilst with the electron transmission efficiency of the grid over 56%, a remarkable high modulated current electron beam over 42mA has been collected by the anode. Also contributed by the high aperture ration of the grid, desorbed gas molecules could flow away from the emission area rapidly when the triode has been operated at a relative high emission current, and finally collected by a vacion pump. The working pressure has been maintained at ∼1 × 10−7 Torr, seldom spark phenomena occurred. Nearly perfect I-V curve and corresponding Fowler-Nordheim (FN) plot confirmed the accuracy of the measured data, and the emission current was long term stable and reproducible. Thusly, this kind of triode would be used as a high-power electron source.

Simulation and Optimization of CNTs Cold Cathode Emission Grid Structure

“…The aperture ratio is used to evaluate the performance of the grid and optimize it, and a grid with an electron transmission efficiency higher than is obtained when the aperture ratio is and the grid wire diameter is m. The results of electron transmission efficiency that we obtained were better than in reference [ 26 ] and in reference [ 27 ]. When the aperture ratio is , the electron transmission efficiency can be maintained between and , even if the grid wire diameter is between 0.01 mm and 0.1 mm.…”

Nano-graphite field-emission cathode for space electric propulsion systems

“…Electrons can be released from such nanostructures by applying a relatively low voltage due to strong field enhancement at their apexes or sharp corners. In most electron guns with thin-film cathodes electrons are extracted using a positively biased mesh located above the cathode [18][19][20]. Emitted electrons travel through the openings in the mesh.…”

Development of a High-Beam-Transparency Gridded Electron Gun Based on a Carbon Nanotube Cold Cathode

“…The small modulator size of gridded electron guns with electrostatic focusing systems offer a little explored solution [20]. Nevertheless, in single grid systems the proportion of the cathode current that is intercepted by the grid can be very high, often in excess of 20-55% [18,19,21,22].…”

“…This unavoidably affects the devices service life. Furthermore, due to the high electric field beneath the grid such sagging can encourage local arc discharge between the cathode and grid which further degrades the devices functional life [21,23,24].…”