| The framing camera is a two-dimensional ultrafast diagnostic equipment with picosecond(ps)temporal resolution,which is obtained the spatiotemporal evolution process of the plasma during implosion fusion in the inertial confinement fusion(ICF)experiments.Currently,the temporal resolution of the pulse-dilation framing cameras is 10 ps,however,with the breakthrough of the ICF experiments and the demand for detecting the more shorter duration process,the diagnostic equipment with the more faster temporal resolution is gradually became hotspot.Therefore,the influence of factors on the temporal resolution performance is analyzed and the ultrafast temporal resolution is studied through building connection among multi-channel control system,picosecond high-voltage pulse generator,and the pulse dilation framing camera temporal resolution performance in the paper.The major research contents are as follows:(1)The model of pulse-dilation framing camera is built by the Monte Carlo method,on which based theory of the finite difference,the photoelectron emission,the fourth-order Runge Kutta(RK4)and the magnetic field imaging,the optimal physical and technical parameters of the model of pulse dilation framing camera with 2 ps are discussed,through analyzing the effects of picosecond high-voltage pulse,the cathode potential and the drift distance.When the cathode potential is-2 k V,the drift distance is 700 mm,the gap between cathode and anode is 1 mm,and the gradient of dilation pulse is 14.8 V/ps,the temporal resolution of the pulse-dilation framing camera is achieved further breaks and reached to1.96 ps.(2)The multi-channel control system is designed using microcontroller technology,the picosecond pulse generator is designed by the Marx circuit with avalanche transistor and the pulse shaping circuit with third-order LC high-pass filter,the picosecond high-voltage pulse is applied to the research of pulse-dilation framing camera temporal resolution by establishing relationship between the control system and the picosecond pulse generator,which is analyzed the influence of the picosecond high-voltage pulse on the technical temporal resolution and the temporal dispersion of space charge effect.When the gradient of the rising edge(dilating pulse)of picosecond high-voltage pulse is ranges from 6 V/ps to14.8 V/ps,the cathode potential is-2 k V,the drift distance is 500 mm and the temporal resolution of the MCP framing camera is 93.8 ps,the technical temporal resolution is range from 7.64 ps to 2.32 ps,and temporal dispersion of space charge effect is range from 89.7 fs to 100 fs.(3)The change rules of the temporal width and radius of electronic pulse is discussed and the model of space charge effect is built using the mean field theory,by which analyzing the influence of pulse-dilation technology and magnetic focusing.The influence of magnetic focusing on the space charge effect is studied through building the model of pulse-dilation framing with difference number of magnetic lenses.When the cathode potential is-2 k V,the drift distance is 700 mm and the gradient of dilation pulse is 14.8 V/ps,the temporal dispersion of space charge effect with the single lens and triple lenses are 89.7 fs and 720.4fs,respectively.(4)The cause of the temporal non-uniformity of the pulse-dilation framing camera is analyzed,which based on the transmission characteristics of electric pulses along the PC.The calculation method of magnification during the transmission process of dilating pulse along the PC is derived,the feasibility of improvement of the temporal uniformity is studied using using pulse superposition technology.When the length of cathode is 60 mm,cathode potential is-2 k V,the drift distance is 700 mm and the gradient of dilation pulse is 11.9 V/ps,the dilation rates of the electron beam at both ends of the cathode are respectively 11.74×and 39.04×,and the relative errors is 232.5%;When the falling edge of the gate pulse is simultaneously loaded in the same direction(with a slope of 12.7 V/ps),the electron beam dilation rates at both ends of the cathode are respectively,11.28× and 14.23×,and the relative errors is 40.21%.which the temporal uniformity is effectively improved.In conclusion,the research results is not only provides the theoretical basis for the development of ultrafast temporal resolution framing cameras with 2 ps,but also provides a new direction for the integration and application of the control technology,high-voltage pulse technology and the ultrafast diagnostic technology;Meanwhile,the new idea of the research of space charge effect is developed in the pulse-dilation framing camera,by which analyzing the influence of magnetic focusing system on the temporal dispersion of the space charge effect;Additionally,the temporal uniformity is significantly improve using the pulse superposition technique,and it provided the new improvement method for temporal uniformity in the pulse-dilation framing camera with large area. |
PDF Full Text Request