Study Of A Compact Large-format Streak Camera

The streak camera,integrating ultra-high temporal resolution,high spatial resolution and spectral resolution,is an indispensable ultra-fast diagnostic instrument in fundamental research such as photo physics,photochemistry,medicine and life sciences,as well as in national strategic technology research such as imaging lidar and inertial confinement fusion.However,up to now,the design of the streak camera is mostly focused on improving its temporal resolution,leaving some disadvantages,such as large volume,bulky,and small effective working area,unaddressed.In this dissertation,an ultra-small streak camera with a large effective working area on the photocathode while ensuring a high spatial resolution and tens of picosecond time resolution simultaneously,is designed and developed.Combining Finite Integration Theory,Particle-In-Cell method and Monte-Carlo method,the smal-size streak tube is designed in a numerical way.And orthogonal experiment method is introduced to improve design efficiency.Also,the orthogonal experimental analysis method is helpful to understand how each part of the system influences its overall performance,which provides a valuable reference in the streak tube optimization.This dissertation successfully designed and developed a state-of-art ultra-small and large-format streak camera.Spherically curved cathode and fluorescent screen are employed to reduce the aberration and the temporal distortion,thus increasing the effective working area and ensuring image resolution of the streak tube simultaneously.A meshless configuration is adopted to lower the risk of electric arc,thus improving the stability and reliability of the tube.To compensate for the shortcomings of the meshless configuration and ensure the temporal resolution of the streak tube,an auxiliary focusing electrode is applied in front of the focusing electrode.The deflectors are a pair of tilted trapezoidal plates to decrease the deflection defocusing effect especially for the fringe electrons,thus meeting the requirement of large detection area.Ultimately,an ultra-compact streak tube has been designed with the dimensions of Φ55 mm × 110 mm,the temporal resolution of 30 ps,the static spatial resolution of 20 lp/mm and the dynamic spatial resolution of 10 lp/mm at the effective cathode working area of Φ28 mm,and the magnification of 1.07.The dissertation,for the first time,thoroughly studied the temporal distortion of streak tube using the numerical method.It shows that the distortion is mainly produced in the cathode-to-deflector region,and it is negligible in the equipotential region.The main influence factor is the radius-of-curvature(ROV)of the spherically curved cathode,and there is an optimum value of the cathode ROV,which minimizes the temporal distortion of the tube.The absolute value of temporal distortion increases with the initial height of photoelectrons emitted from the cathode.In addition,the slit image curvature in the dynamic experiment is also caused by temporal distortion.The smaller the temporal distortion,the smaller the imaging curvature.According to the tube design,a small-size streak tube is manufactured and tested,including the fabrication of each electrode,the fabrication of high conversion efficiency fluorescent screen,the fabrication of photocathode with high sensitivity and uniformity,and the assembly of the tube.An experimental test platform is built to test the static performance of the tube.It shows that the image distortion of the tube is quite small,the photocathode radiant sensitivity and output non-uniformity is good.The magnification of the tube is approximately 1.The static spatial resolution reaches 20 lp/mm over the entire Φ28 mm photocathode working area,which is in good agreement with the simulation.According to the performance parameters of the streak tube,the key performance of the imaging lidar system based on this streak tube is theoretically analyzed.The effective cathode working area of streak tube plays a key role in the resolution,depth of field(DOF)and azimuth field of view(FOV)of imaging system.The spatial resolution and range resolution of lidar are negatively exponential to the effective working area of the tube,and the azimuth FOV and the DOF are inversely proportional to the effective working area of streak tube.