Study On Imaging Quality Of Short Magnetic Focus Converting Tube

Framing cameras have the functions of photoelectric conversion,pulse gating,and image enhancement for images,and are the main tools for studying ultra-fast phenomena.In the final stage of Inertial Confinement Fusion(ICF),the target nucleus will be compressed to several tens of micrometers.Because the short-magnet-focusing framing camera has a micron-scale two-dimensional spatial resolution,it is suitable for ICF diagnostic studies.In order to better meet the requirements of high-altitude resolution ICF diagnostic tests,this paper further explored the short magnetic focusing image tube which is developed by our group.Compared to the long magnetic lens tube of LLNL in the United States,short magnetic focusing has the advantages of easy operation,adjustable imaging magnification,and low excitation current.However,the research on short magnetic focusing lenses still needs further research.So our group focuses on the imaging quality of the short-magnification lens time-spreading and amplitude-division imaging tube.Because the magnetic lens plays a role in focusing electron beams in the splitter tube,The key role of electron beam focusing directly affects imaging results.In this paper,under the imaging magnification of 1:1,the structure and imaging conditions of the magnetic lens of the short magnetic focusing system are tested and simulated.The experiment is carried out by building a short magnetic focusing system;and the simulation is performed by Lorentz 3D-EM software.This dissertation studies the structure of the magnetic lens are including the gap size of the magnetic lens and the influence of the combination of single and double magnetic lenses on the spatial resolution.This paper discusses the imaging conditions,includes the distance between the cathode grid,the cathode grid acceleration voltage,and the magnetic lens excitation current.The imaging quality of this paper mainly includes three aspects of discussion:first,spatial resolution;second,imaging distortion;and third,image rotation angle.Mainly for the following considerations:the spatial resolution directly measures the spatial resolution performance of the system;imaging distortion affects the clarity of the image after imaging;like the rotation angle will affect the integrity of the obtained image;thus for these three Systematic considerations can be used to more fully analyze the imaging quality of short magnetic focusing lenses.The simulated average of the analogy of the corner is77.26~o,the experimental measurement is 71.0~o,and the magnetic flux leakage of the system is 45 Amps.The measured results of the distortion are obtained by the experimental measurement of the single and double magnetic lens system at the off axis of 6mm.The imaging distortion rate was 2.4%and 0.9%,respectively,and it was8.5%and 3.2%at 12mm off-axis.The innovations of this thesis are:1.Study the problem of the image rotation angle of the short magnetic focusing lens and the resulting leakage magnetic flux phenomenon.2.To study the imaging distortion of the short magnetic focusing lens,and to confirm that the dual magnetic lens imaging system can reduce the imaging distortion effect on the short magnetic focusing amplitude-dividing imaging tube.The purpose of this dissertation is to find a way to effectively improve the spatial resolution performance of the short-magnet-focusing split-rate imager,to obtain better imaging results,and to provide a super-high spatial resolution performance for the study of Chinese ICF quick diagnostic equipment.