Speaker
Description
A portable X-ray generator for plant root imaging is being developed. The generator mainly includes a Cockcroft-Walton DC high voltage generator, which provides a high voltage DC bias to an x-ray diode, and a metallic target to convert the electron beam into X-rays. A backscatter imaging technique is used, where X-rays are projected onto the plant target (the roots buried in soil), and Compton scattered photons are collected to reconstruct an image. To reduce the size and complexity of the X-ray generator, cold cathodes are desired to avoid the need for cathode heating. Ex-situ fabricated carbon-nanotubes (CNT) deposited on silicon wafers have been chosen as a potential cathode considering their high field emission efficiency and physical and chemical stability. Preliminary tests of CNT field emission cathodes for use as the electron beam emitter in the X-ray diode are presented. CNT cathodes have been shown to produce a current with a magnitude of 100 µA with a relatively low turn-on voltage. Compared to thermionic sources of electrons, field emission-based carbon nanotube cathodes appear to be a very good candidate electron source for our X-ray generator.
Work supported by the Advance Research Projects Agency-Energy
