Research On Key Technologies Of X-ray Femtosecond Streak Image Camera

Owing to the excellent feature of ultrahigh temporal resolution, femtosecondstreak image camera has been the indispensable scientific instrument of ultrafastdiagnosis technique. Aim to meet the ICF demand, a new X-ray femtosecond streakimage camera with both high temporal and spatial resolution was designed anddeveloped.On account of all the factors that may influence the performance, a streak imagetube has been optimally designed. To improve its integrated performance, a pair oftraveling wave deflectors is located before a magnetic solenoid lens in the tube,which minimizes the electron transit time from anode to deflection plates andtherefore reduces time dispersion and space charge effects. Using CST softwareparticle studio, a pair of traveling wave deflectors with wide bandwidth has beendesigned, which is beneficial to slow down the electrical deflecting pulse to matchthe beam velocity in a wide frequency range, and improve the deflection sensitivity.Furthermore, a series of electrical and structural parameters of the magnetic solenoidlens in the tube have been calculated optimally, which strengthens the spatialfocusing ability. After tracing the trajectory of electrons and calculating themodulation transfer function, we get physical temporal resolution of189fs andspatial resolution of photocathode center above100Lp/mm. Based on the aberrationtheory, the imaging quality of streak image tube has been evaluated systematically.Based on the analysis above, the X-ray femtosecond streak image camera hasbeen developed, involving a photocathode, the magnetic solenoid lens, a pair oftraveling wave deflectors, and a sweep circuit based on GaAs photoconductiveswitch.The static testing platform and dynamic testing platform have been built,including Ti: Sapphire femtosecond laser system, M-Z interferometer, X-rayfemtosecond streak image camera, a vacuum pump system, a set of high-voltagepower supply, and an autocorrelator. The testing experiments are carried out, and theresult shows that the static spatial resolution is higher than35Lp/mm, dynamicspatial resolution is above25Lp/mm, dynamic temporal resolution is about0.975ps,the amplification ratio is2.2, and the gain is higher than13000.The characteristics of the X-ray femtosecond streak image camera are listed below:1. First, a new femtosecond streak image camera with both high temporal andspatial resolution has been put forward, which will play an important role in the fieldof ICF.2. The new streak image tube, in which a pair of traveling wave deflectors islocated before a magnetic solenoid lens has been adopted, while the space chargeeffect has been restrained, all that will improve the temporal and spatial resolution.Its small jitter can not be measured by the oscilloscope used in the paper.3. A pair of traveling wave deflectors and a magnetic solenoid lens have beenoptimally designed, which broadens the bandwidth, and improves the deflectingperformance and spatial focusing ability. In order to reshape electron trajectory, a slithas been inserted after an acceleration mesh as a diaphragm.4. A new sweep circuit based on GaAs photoconductive switch has beendeveloped and tested. The test results show that the voltage ramp is faster than10kV/ns, which meets the requirement of the streak image camera.5. The static testing platform and dynamic testing platform have been built, andcharacteristics calibration for an X-ray streak camera has been carried out. Finally,the width of femtosecond laser pulses has been measured by an autocorrelator.