Development Of A High Deflection Sensitivity Synchroscan Streak Tube

As the only linear diagnostic equipment which can directly detect ultra-fast repetitive weak light signals with the advantages of femtosecond-picosecond temporal resolution,micro-scale spatial resolution,high detection sensitivity and intuitive real-time,the synchroscan streak camera plays a particularly important role in the research of basic sciences such as photobiology,photochemistry and condensed matter physics,as well as applied sciences such as laser,optical communications and biomedicine.Considering that the current synchroscan streak tube developed by different units and scientific research institutes at home and abroad has either a relatively small effective cathode size,or a relatively low spatial resolution or deflection sensitivity.In this paper,under the premise of taking into account the effective working area of the cathode and the space-time resolution capability,an equal-diameter cylindrical synchroscan streak tube with a deflection sensitivity of125mm/k V is designed by rationally designing the voltage between the cathode and the anode and increasing the distance between the deflection plate and the phosphor screen.The high deflection sensitivity can reduce the amplitude of the scanning voltage required to deflect the electron beam at the same distance on the image surface,and can effectively reduce the difficulty of the implementation of synchronous scanning circuit,which is of great significance to improve the time resolution performance of synchroscan streak camera and reduce the difficulty of preparation.Based on a large amount of literature research and comparative analysis,this paper firstly determined the design scheme of each electrode’s structure of this streak tube and discussed the relevant consideration factors in the design process in detail.The final designed streak tube consists of a plane cathode plane grid,two focusing lens systems,two pairs of parallel plate deflection systems perpendicular to each other,a shell and a phosphor screen and has a total length of 306.2mm.Then,by analyzing the influence law of each focusing electrode voltage on the imaging quality of the streak tube and calculating the magnification under different electrode voltages and the deflection sensitivity under different working voltages,a set of optimal voltage parameters with a working voltage of-7000 V was optimized.And then,based on the optimized voltage parameters,through detailed analysis of the field distribution changes in the streak tube,the reasons for the changes in the motion state of the photoelectrons in different regions of the streak tube are explained.Finally,combined with evaluation methods such as modulation transfer function and Rayleigh criterion,a series of simulations and experimental analysis are carried out to illustrate the effectiveness of the synchroscan streak tube from multiple angles such as time resolution characteristics,spatial resolution characteristics,and deflection characteristics.The simulation results under-7000 V working voltage with the aid of Computer Simulation Technology software show that the deflection sensitivity of the streak tube is 125 mm/k V,the physical temporal resolution is better than 1.83 ps @MTF=10%and the static spatial resolution on the photocathode is better than 38 lp/mm @MTF=10% over the effective photocathode area with a size of 10 mm×4 mm.And by applying a synchronous scanning voltage with a repetition frequency of 250 MHz on the deflection electrode,the results show that the dynamic spatial resolution of the streak tube is better than 16 lp/mm,the limit of the dynamic temporal resolution is1.39 ps,and two rectangular electron pulses with a size of 10 mm×20 μm and an interval of 2.3 ps emitted from the photocathode at can be well resolved by the streak tube.Moreover,Experimental measurements were conducted with a streak tube developed in our laboratory.The results demonstrate that the streak tube can response in the entire visible light band,and its photocathode luminance sensitivity is greater than 208μA/lm.The static spatial resolution is 40 lp/mm at the center of the photocathode.The temporal resolution is 5.55 ps measured under a synchronous scanning voltage with a repetition frequency of 75 MHz.