Oil-Free Compact X-Ray Generator Based on Carbon Nanotube Field Emitters

Designing an efficient, durable, lightweight, and compact X-ray generator is most challenging to the field of medical imaging. The most possible way to develop an efficient compact X-ray generator is by using (1) carbon nanotubes (CNTs) as electron field emitters over conventional thermionic sources which results in high temporal and spatial resolution. Tunneling of electrons from the tip of the nanotubes due to the high local electrical field makes CNTs an ideal material for compact portable X-ray generator [1,2], (2) ceramic envelop for X-ray tube over conventional glass tube offer not only reduction in tube size and ceramic-metal hermetic sealing but also provide high electrical insulation [3-5], and (3) lightweight polymeric-material instead of transformer oil which prevents arcing from all high voltage surfaces and provide high voltage insulation. In this study, we report the design, fabrication, and characterization of an oil-free-CNT-enabled compact X-ray generator in which X-ray tube sealed by the ceramic body instead of glass. The whole unit was compacted with polymer-based material instead of transformer insulating oil in order to make a compact X-ray generator more lightweight and handheld. CNTs were synthesized directly on a metal alloy substrate by the chemical vapor deposition (CVD) method and characterized by Raman spectroscopy, SEM, and TEM. Those grown CNTs were assembled with a gate and a focuser and then combined into an electron gun (e-gun) through a brazing process. By using this device, high-resolution X-ray images were obtained at an accelerated voltage ranging between 40–70 kV by digital switching control amid emitter and anode.<br/><b>References:</b><br/>1. Jeong J.-W., et al., A vacuum-sealed compact X-ray tube based on focused carbon nanotube field-emission electrons, Nanotechnology. 24 (2013) 085201.<br/>2. Jeong J.-W., et al., A digital miniature X-ray tube with a high-density triode carbon nanotube field emitter, Appl. Phys. Lett. 102 (2013) 023504.<br/>3. Hartl W., et al., A metal/ceramic diagnostic X-ray tube, Philips Tech. Rev. 41 (1983) 126-134.<br/>4. Hartl W., et al., Metal/ceramic X-ray tubes for non-destructive testing, Philips Tech. Rev. 41 (1983) 24–29.<br/>5. Gupta A.P., et al., Compact X-ray tube with ceramic vacuum seal for portable and robust dental imaging, IEEE Trans. Electron Devices. 68 (2021) 4705-4710.