Research Of Miniature X-ray Source

X-ray has been widely used in industry and medicine since it was found in 1895, such as nondestructive detection of cavities in objects using X-ray' s property of penetration, trace element analysis using x-ray fluorescence, radiation therapy using X-ray' s ability to damage protein, and so on. However, the most commonly used X-ray sources didn' t change much no matter in structure or theory, still using thermionic cathodes as electron sources. Such conventional X-ray tubes have some defaults, such as big volume, low frequency response, demanding for supply to cathode that was also brittle. Now all those disadvantages are to be solved by using field emission cathode.New technologies and materials made field emission cathode possible and applicable. In 1976, spindt cathode was firstly prepared by C. Spindt. In 1991, carbon nanotubes(CNTs) was firstly found by Iijima. S. Both of two cathodes were called field emission cathodes having a great number of tips in their surfaces from which the electrons can go out at common voltage and room temperature. Using field emission cathode, X ray source can be made with several advantages: smaller volume and brighter, high frequency response, in-time turning on, etc.Considering of the merits and potential markets, researching and fabricating miniature X-ray source is meaningful. Using finite element method, theory analyses were firstly made. Static-electric field of spindt cathode was analyzed and then field emission current was simulated. The method could direct the fabrication of spindt cathode. How the aspect ration and site density of CNTs effect the field enhancement factor were also analyzed.At last an experiment X-ray source equipment was constructed using CNTs as cathode. The field emission of CNTs was measured and Cu' Ka spectrum was detected. Those implied that practical miniature X-ray source could be accomplished.