Design And Fabrication Of Carbon Nanotube Cold Cathode Microfocus X-ray Tube

With the development of science and technology,there have involved the demand for micro-size imaging,such as X-ray microscopic analysis and manipulation of biological cells,the non-destructive testing of material lattices.It has been difficult to meet these requirements for general focal spot size X-ray sources.Therefore,the market has an urgent need for microfocus X-ray tubes.Although the traditional hot cathode microfocus X-ray tube can meet the requirements to a certain extent,it has such disadvantages as slow start-up speed,short working life,large equipment volume,insufficient time and space resolution,and the like.As an ideal field emission electron source,carbon nanotubes are used as cathodes of X-ray tubes,which are expected to make up for these shortcomings of hot cathodes.The carbon nanotube cold cathode microfocus X-ray tube has many advantages such as small volume,fast response,high resolution,long working life,small radiation dose,etc.It will be expected to become a new generation of X-ray tube.In this paper,microfocus X-ray tubes using carbon nanotubes as cathodes will be studied in order to successfully realize microfocus X-ray tubes with fast response,small focal spot size,stable operation,and excellent imaging results.The research goal is to achieve a cold cathode microfocus X-ray tube with an operating current of 20?A and a focal diameter of less than 20?m at an anode voltage of 80 kV.The main research work of this paper has the following two aspects:(1)Preparation of carbon nanotube cathode emitters with excellent performance by MWPECVD;by examining the influence of lithographic parameters on the pattern,optimizing the lithography process and achieving high quality lithographic patterns;by increasing the thickness of the plated metal layer,increasing Adhesion of carbon nanotubes to the substrate.The sophisticated testing of the carbon nanotube emission source enables the carbon nanotube emission source to operate stably with an emission current of 100?A.Analyze the experience and test results.The highest measured field emission current density reached 80.9 A/cm~2.(2)Design and optimize the electron optical system of the microfocus X-ray tube.In order for the electron beam to focus on the anode target surface,the electron optical system in the X-ray tube needs to be optimized.In this paper,the effects of the grid,the first focusing electrode,and the second focusing electrode on the focusing effect of the electron beam are studied,and a preliminary analysis is performed.Finally,an electron beam focusing structure with a focal diameter of 20?m is realized.(3)The imaging function of the microfocus X-ray tube was tested using an X-ray imaging system.Memory sticks and chips were magnified and imaged.It can also image objects of 16?m size.