Plasma-induced field emission and plasma expansion of carbon nanotube cathodes

Abstract

High intensity electron emission cathodes based on carbon nanotube films have been successfully fabricated. An investigation of the explosive field emission properties of the carbon nanotube cathode in a double-pulse mode was presented and a high emission current density of 245 A cm−2 was obtained. The formation of the cathode plasma layer was proved and the production process of the electron beams from the cathode was explained. The time and space resolution of the electron beams flow from the cathode was investigated. The plasma expanded at a velocity of ∼8.17 cm µs−1 towards the anode and influenced on the intensity and distribution of electron beams obviously. The formation of cathode plasma had no preferential position and the local enhancement of electron beams was random. This carbon nanotube cathode appears to be suitable for high-power microwave device applications.

Investigation on the Plasma-Induced Emission Properties of Large Area Carbon Nanotube Array Cathodes with Different Morphologies

“…The relationship between the emission currents and the number of pulses for the four kinds of arrays is presented in Figure 3b . Along with the continuance of the pulse emission, the CNT arrays would lose the emission ability gradually [ 13 - 15 ]. The results show that after 80 pulses, the emission currents of the four kinds of CNT array have about from 11.3 to 12.9% reductions.…”

“…The CCD images show the spatial distribution of the emission sites and the plasmas. The distribution of the emission sites on the CNT arrays is very similar to that of the coated CNT cathode [ 12 , 13 ]. Figure 4a is the CCD image of the 4-μm height cathode.…”

“…Then, the CNT array cathodes were used to next plasma-induced emission tests under the pulse electric field. The high-voltage pulse emission experiments were performed in a diode powered by a pulse-forming network generator at background pressure of 5×10 -4 Pa [ 12 , 13 ]. The generator has an output double-pulse with about 100-ns duration, and the interval between two pulses was about 400 ns.…”

Vacuum Outgassing Behavior of Carbon Nanotube Cathode with High-Intensity Pulsed Electron Emission

“…According to the experimental data statistics, a positive correlation is found between the cathode emission current and the brightness and area of the luminescent zones. In conclusion, the high-intensity electron emission mechanism of CNT cathode is the PFE [14,19] , the CNT's outgassing makes it possible for the plasma emission.…”

Plasma-induced field emission study of carbon nanotube cathode

“…The field emission current density only reached A=cm 2 $ mA=cm 2 . Some studies were focused on intense current field emission properties of CNTs for application in linear induction accelerators (LIAs) [15][16][17] and high power microwave tubes [18,19]. The field emission current density can reach hundreds of A=cm 2 .…”