| X-ray can pass through the surface of the object and capture the inside image,which has been wildly used in the medication,industry and security.Field emission X-ray tube can achieve fast imaging by using the electric field to modulate the cathode electron rapidly,which has great potential in low dose X-ray imaging or dynamic monitoring.Thus,this paper has focused on the influence of the electron modulation structure on the anode current.The improvement of driving method,gate structure was presented in this paper,and optimal parameters of gate mesh has been proposed according to simulations results,and imaging experiments have also been performed with the x-ray tube which we designed.We did the emission experiment of both driven by direct voltage and pulsed voltage.The result show that the pulsed-voltage-drived method can enlarge the anode current,however,when the current is large,the electron transmittance from the gate became very low,which limited the anode current.Two solutions are proposed to solve the problem.The first is using the second electron emission material MgO to enlarge the anode current.The experimental result shows that the MgO can largely improve the anode current.The second is using the carbon thin film,which can improve the uniformity of the electric field between the gate and the cathode.The experiment result show the electron transmittance can be hold still and the anode current can be larger.In order to optimize the gate mesh parameters,three kinds of mesh shape also studied.The optimal size of mesh gate is achieved by simulation result,with the triangle of 0.4mm edge length and the electron transmittance reach in 68.7%.Finally we fabricated an X-ray tube and implemented the imaging experiment with our x-ray tube.Clear x-ray images were obtained both driven by the direct and pulsed current,and images were even captured under a narrow pulse of 50ms.We also used a SEM to research some factors which can have influence on the imaging quality for the later study. |
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