Carbon Nanotubes-Graphene Hybrid Array For The Micro Focus X-Ray Tube

With the higher requirement of the resolution, penetration imaging capabi lity and the accuracy of the test results, the micro focus X-ray tube enter into vision of the public. The micro focus X-ray tube is widely used in biomedical, industrial, materials science and many other microscopic fields on account of its micrometer scale of the point light source, outstanding imaging quality and high resolution.Most of performance of the field emission cold cathode micro focus X-ray tube are much higher than thermal cathode electron source, such as small volume, low turn-on voltage, low power consumption, stable work, long lifetime and so on. Even though the carbon nanotubes with nanoscale tip radius of curvature has already been recognized as the best choice for field emission, carbon nanotube cold cathode field emission current density is relatively low, which is not solved until now.This paper attempts to introduce a new material graphene with high electrical conductivity, high thermal conductivity, high strength, high electron mobility. We try to improve the problems and limitations of the field emission of carbon nanotube cathode by creating carbon nanotubes and graphene composited structure cathode array with the method of ME-PECVD, lithography, transfer. Meanwhile, the 3D electromagnetic simulation software has been used to design and optimize to meet the requirements of the micro focus X-ray tube. The main researches are as follows:(1) The method of the preparation of carbon nanotube field emission cold cathode array was studied systematically. At the same time, we try to explore the problems and limitations of carbon nanotube field emission and seek the solutions through summing the factors affecting the field emission properties of carbon nanotubes based on the stable preparation technology.(2) The graphene material is introduced into the carbon nanotube field emission cold cathode array. The carbon nanotubes and the graphene composited structure array will be prepared through summing the method and technology to improve the capability of field emission. There are six schemes in total, including graphene which grows on the different metal catalyst substrate Ni and Cu by MW-PECVD and transferred graphene directly on the substrate, then we prepare the carbon nanotube on the graphene to finish the composited structure array. Field emission characteristics of CNT emitter array shows that the carbon nanotubes and the graphene composited structure point array based on Ni catalyst is the best of all above six projects, low turn-on electric field and the current density reached 1.57A/cm2.(3) The 3D electromagnetic simulation software Vector Opera has been used to design and optimize the micro focus X-ray tube electron gun. Such parameters as geometrical distance, size, location and applied voltage among all the electrodes are considered respectively in relation to the size of X-ray focal spot. Finally, we obtain a small focus size of 38μm×38μm after analysis the law by simulating and optimizing.