Research On The Picosecond High Voltage Pulse Applied To Framing Camera

The framing camera based on the microchannel plate(MCP)is a two-dimensional ultra fast diagnostic equipment with picosecond temporal resolution.It is universally applied to measure the space-time evolution of high-temperature and high-density plasma in the Inertial Confinement Fusion(ICF)experiments.In the framing camera,the electron transit time and its time dispersion in the MCP channel are the main factors that restrict the temporal resolution,and are closely related to the physical structure of the MCP and the picosecond high voltage gating pulse.Although the temporal resolution can be improved by thin MCP,it is difficult to be widely used because of its poor signal-to-noise ratio and high processing requirements.Therefore,the study of picosecond high-voltage gating pulse is of great importance to improve the temporal resolution of the MCP framing camera.For this reason,nanosecond high voltage pulse circuit and pulse shaping technology are combined to design picosecond high voltage pulse by this paper,which is applied to the study of temporal resolution of the MCP framing camera and provides a new idea for the application of high voltage pulse technology in the field of ultra-fast diagnosis.The following three parts are mainly included by this paper:(1)Two kinds of nanosecond high voltage pulse generators are designed by using the Mark circuit of avalanche triode and Drift Step Recovery Diodes(DSRD)based on the generation principle of nanosecond high voltage pulse.By analyzing the influence of circuit structure and component parameters on the output pulse performance,the nanosecond high voltage pulse with amplitude of-6.058 k V and half-height width of165.924 ns,and with amplitude of-6 k V and half-height of 18.5 ns are obtained,respectively.(2)Pulse shaping and filtering circuit are designed by using self-breakdown steepening switch and Sallen-Key(SK)filter technology,and three picosecond high voltage pulse generators are constructed by combining nanosecond pulse generators based on the principle of generating picosecond high voltage pulse.There are picosecond high voltage pulse generators based on Mark and self-breakdown steepening switch,picosecond high voltage pulse generators based on DSRD and self-breakdown steepening switch,and picosecond high voltage pulse generator based on DSRD and SK filter technology is developed.By analyzing the influence of pulse shaping and filtering circuit structure and component parameters on picosecond pulse,picosecond high voltage gating pulses with amplitude of-2.8 k V and half-height width of 124 ps,amplitude of-2.51 k V and half-height of 166 ps,and amplitude of-2.56 k V and half-height of 466 ps are obtained,respectively.(3)The photoelectron dynamic multiplication model in the MCP channel is established by Monte Carlo method,and three picosecond high voltage pulses are loaded on the model through the energy and emission angle distribution of cathode photoelectrons and their secondary doubled electrons,the secondary electrons amount and the incidence angle distribution based on the structure of the MCP framing camera and the multiplication characteristics of the MCP.The MCP gain at different time of the gating pulse is counted and the time-gain curve is established.The temporal resolutions of the MCP framing camera are 53 ps,59 ps and 169 ps,respectively.In summary,through the study of the above work,the paper not only integrates the avalanche triode and DSRD into the design of nanosecond pulse circuit,but also provides a new idea for the development of nanosecond pulse generator.The design of picosecond pulse generation circuit using self-breakdown steepening switch and SK filter provides a new way to expand the application of the two devices.In addition,the application of picosecond high voltage pulse to the time resolution of MCP framing camera provides a new method for the fusion of high power pulse technology and ultra-fast diagnostic technology.