Theoretical And Experimental Research On Femtosecond Temporal Resolution Streak Camera

As the only diagnostic equipment which has sub-picosecond temporal resolution，femtosecond streak camera has been one of the hottest research topic in the field ofultrafast diagnostic technology in recent years. In this paper， a magnetic focusingfemtosecond streak tube with prepositive traveling wave deflector was designed anddeveloped. The measured static spatial resolution of the streak tube can reach more than30lp/mm， while the dynamic spatial resolution is expected to reach250fs.Based on comprehensive considerations of the main factors affecting the timeresolution of the streak tube， a new magnetic focusing femtosecond streak tube witha prepositive traveling wave deflector was designed， and the structure parameters ofthe traveling wave deflector and the magnetic focusing lens were optimized in the CSTMicrowave Studio and Electromagnetic Studio respectively. In order to further verifythe performance of streak tube from the theory， trajectories of large numbers ofelectrons emited from surface of the photocathode were tracked， which was followedby statistical analysis of the position distribution and transit time.Then，the point spreadfunction and modulation transform function were calculated，which made it possibleto evaluate the performance of the streak tube.The calculation results show: the limitphysical time resolution is190fs， the size of the effective area on the cathode reaches5mm， the static spatial resolution and physical temporal resolution turns out to bebetter than35lp/mm、300fs@5mm slit，while the dynamic temporal resolution is500fs@5mm×5um slit. The limit dynamic temporal resolution， calculated throughtracking electrons emited from center of the cathode turns out to be250fs.The femtosecond streak tube desiged in this paper need high slope of sweepvoltage ramp (>10kV/ns) and weak time jitter (<100fs)， which can not be met bytraditional sweep circuit. In this paper， a new bilateral sweep circuit based onphotoconductive semiconductor switch was developed and tested. The test results showthat the voltage ramp is faster than10kV/ns， and the time jitter is too weak to bemeasured by oscilloscope used in this paper. Finally，the femtosecond streak tube designed in this paper was fabricated andtested. The results show that the static spatial resolution of the streak tube can reachmore than30lp/mm.