Fast microfocus x-ray tube based on carbon nanotube array

A full vacuum-sealed macrofocus x-ray tube with a vertically-aligned ring-shaped carbon nanotube (CNT) emitter grown by microwave plasma enhanced chemical vapor deposition is presented in this paper. The external grid allowed the CNT-based x-ray tube to exhibit transient switching on and off. The total emission current was 200 mu A, which corresponds to a maximum emission current density of 10.1 A/cm(2) from the ring-shaped CNT emitter when the grid voltage was 2.4 kV. The optimized focus electrode controlled the beam convergence on the target to produce a very small x-ray focal spot size less than 5 mu m. Consequently, this microfocus x-ray tube could produce x-ray images with very high spatial resolution. X-ray fluoroscopy images of a multilayer printed circuit board (PCB) and field programmable gate array show distinct gold PCB traces with approximately 20 mu m width. Published by the AVS.