| The X-ray phase-contrast imaging method can obtain more image information of light element substances than the absorption imaging method,and has a wider application prospect..The grating-based phase-contrast imaging method is the most likely method to be used in real life among various methods of obtaining phase-contrast images,but this method requires the use of analysis gratings with a large area and a small periodic structure,and the production of gratings with such structures has always been a worldwide problem.The method of X-ray phase-contrast imaging based on the inverse Talbot-Lau effect proposed in 2009 can effectively reduce the difficulty of grating fabrication.The X-ray source used in this method is a cone beam light source,and the absorption grating area is proportional to the distance between the grating and the light source.Based on this situation,the source grating is directly fabricated on the Xray light source,which reduces the number of required gratings and shortens the system length.This thesis starts with the design of the micro-structure focal spot X-ray tube,first proves the feasibility of the micro-structure focal spot X-ray source from a theoretical point of view,and selects the appropriate line-gap width ratio according to the effect of the duty ratio on the image contrast.When the line-gap width ratio is 0.7 ～ 2.3,the image contrast is the highest.According to this line-gap width ratio,a reticle for UV lithography is designed.Secondly,the anode exit mode is selected.By analyzing the advantages and disadvantages of the two exit modes,the transmission is selected.The formula is used as the X-ray emission method;then,according to the properties of each substance and the efficiency of generating X-rays,tungsten is selected as the anode target material,and conductive diamond is used as the material of the anode body;finally,the anode target is designed from the perspective of the X-ray absorption of the substance Thickness,the thickness of the obtained anode target was 2 μm.Starting with the production of micro-structured focal spot X-ray tubes,firstly,according to the advantages and disadvantages of various cathode emission methods,direct-heating hot cathode emission is selected as the X-ray tube cathode emission method,combined with the shortcomings of the existing hot cathode emission structure design a new planar cathode structure;then choose a suitable process to make the micro-structure anode.In view of the fact that the electron beam photoresist colloid is too thin and the single-layer glue process cannot produce the structure we want,we choose the double-layer glue process.Combined with the magnetron sputtering process and the stripping process,the micro-structured anode is made.The top adhesive of the double-layer adhesive process is positive photoresist HTI751,and the bottom adhesive is the non-photosensitive LOR30 B.The final parameters of the double-layer adhesive process are LOR30 B.Soft-bake at 180℃ for 5min,HTI751 photoresist using 150℃ before baking for 150 s,110℃ after baking for 120 s,using MA6 UV mask exposure machine for 3.5s;by measuring the thickness of the coating at 10 min,the thickness of sputtering is 2μm Tungsten film needs25min;finally,according to the existing X-ray tube structure,design a suitable package structure,explain the difference between the structure and the original structure,and explain the advantages of the structure.The development of the new micro-structured focal spot X-ray tube will promote the development of X-ray phase-contrast imaging technology and promote the application of X-ray proportional technology in industrial and medical fields. |
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