Figure 1.

Schematic diagram, SEM image, photograph, and X-ray radiograph. (a) Schematic diagram of the vacuum-sealed miniature X-ray tube. (b) SEM image of the CNT cathode. (c) Photograph and (d) X-ray radiograph (XR) of the fabricated miniature X-ray tube. The XR has been taken by a microfocus X-ray imaging system (Nikon Metrology XTV160, Nikon Co., Shinjuku, Tokyo, Japan).