Two applications of carbon nanotube paste emitters: nano-focus, and high-flux vacuum-sealed x-ray tubes

The printed carbon nanotube (CNT) paste emitters were applied to two types of vacuum-sealed x-ray tubes for several hundred-nanometer-resolution non-destructive testing (NDT) and cone-beam breast computed tomography (CB-BCT) applications. A single dot CNT emitter of 200 micrometer in diameter was made for a small focal spot size of NDT imaging meanwhile a 983-dots array was for a high current of CB-BCT imaging. The electron beam emitted from the single dot emitter in the nano-focus x-ray tube is strongly focused to a small focal spot size of 1 micrometer or less in diameter by help of electrostatic and magnetic focusing lenses, and the 983 emitters produce a large field emission current over 200 mA with a moderate focal spot, tentatively applicable to CB-BCT imaging. The printed CNT emitters can be used for a variety of electron sources from several hundred-nanometer focusing to high-flux xray tubes.