Visualization of emitting sites on carbon fiber cathode by surface treatment in high-current vacuum discharge process

In this paper, a carbon fiber cathode, having robust, easily shaped, and epoxy-free properties, is constructed by squeeze casting technique that can overcome some disadvantages of conventional methods. Carbon fiber emitters on the cathode surface had a high distribution density, thus ensuring sufficient emission centers or emission uniformity. The fabricated cathode was tested in a diode powered by a ∼350 kV, ∼40 Ω, ∼400 ns high-voltage pulse generator. The turn-on electric field was estimated to be ∼50 kV/cm, and the field enhancement factor was (1.2-2.0) × 103. It was found that the electron emission of carbon fiber cathode is initiated from the individual bright spots at a current density of up to 400 A/cm2. Most notably, the X-ray images of electron beam on anode foil demonstrate the development of bright spots on the cathode surface. As a whole, this class of cathodes can endure high-current pulsed emission, and has a positive application prospect.