摘要
为获得高幅值和窄半高宽的选通脉冲,基于雪崩三极管Marx脉冲发生器和脉冲陡化技术,设计皮秒高压脉冲电路,对应用于分幅相机的选通脉冲展开研究,并采用蒙特卡洛法建立微通道板通道内的光电子动态倍增研究模型,通过将选通脉冲应用于微通道板增益计算获取时间分辨率。研究结果表明,基于Marx脉冲发生器和脉冲陡化技术相结合产生皮秒选通脉冲的方法是可行的,当Marx脉冲发生器为三级,脉冲陡化电路的两个电感和电容分别为725 nH、7 nH、1 pF时,可获得幅值-2.8 kV和半高宽124 ps的选通脉冲。将该选通脉冲加载于微通道板上进行光电子动态倍增过程研究,通过分析和统计微通道板增益,获得分幅相机的时间分辨率约为53 ps。
Inertial confinement fusion is the main way to obtain experimental data of thermonuclear weapons. Since the Microchannel Plate(MCP) framing camera has picosecond-level temporal resolution and micron-level spatial resolution in the inertial confinement fusion experiment, it can effectively detect the plasma space-time evolution state of the Inertial confinement fusion process. The temporal resolution of the MCP framing camera is about 60~100 ps. The main influencing factors are the electronic transit time and its dispersion in the MCP channel. There are two main improvement methods: the thin MCP and optimized gating pulse. Although thin MCP can effectively improve the temporal resolution of the camera, it is difficult to be widely used due to the poor signal-to-noise ratio and high manufacturing process requirements. Therefore, the improvement of the temporal resolution of MCP framing cameras is commonly achieved by optimizing the circuit structure to obtain high-amplitude and narrow half-width picosecond gating pulse. High-voltage gating pulse with picoseconds is a branch of pulse power technology.Firstly, it usually stores low-power energy, and then releases energy to output high-power pulses in a very short time. The picosecond gating pulse applied to MCP framing camera can be realized by nanosecond high voltage pulse and pulse shaping. In terms of nanosecond high-voltage pulse, avalanche triodes are widely used in pulse generators due to their fast turn-on switching characteristics in avalanche states.However, under different circuit structures, high-voltage discharge ignition and easy breakdown can occur.In terms of pulse shaping, the output of picosecond pulse is usually realized through special line forming and pulse steepening technique. The former achieves a substantial reduction in pulse time width and power by compressing the pulse energy, while the latter achieves pulse time width compression by steepening the front and rear edges of the pulse, which has a relatively little impact on pulse power. The temporal resolution of the framing camera refers to the gain-time curve half width of the MCP. In order to calculate the temporal resolution, a gating pulse is usually loaded on the MCP to study the photoelectron dynamic multiplication process in the MCP channel to calculate the electron gain, so as to draw the MCP gain-time curve. In this paper, Marx pulse generator is designed based on avalanche triode firstly, and the influence of circuit parameters on the output nanosecond pulse is analyzed. Marx generator is a common device used to obtain high amplitude and nanosecond half width pulses in pulse power technology. The n-stage Marx pulse generator is designed in a mixed mode of avalanche triode series and parallel connection. The avalanche breakdown voltage of the avalanche triode 2N5551 is about 480 V, which is used as a switch for the generator. In order to achieve a high amplitude output of the pulse generator and reduce the circuit complexity, it is required that each stage of the generating circuit should be connected in series with multiple avalanche triodes as much as possible to improve the output amplitude. However, due to the situation that too many avalanche triodes in series can lead to high-voltage ignition and reduce the stability of the generator, the number of avalanche triodes at all levels should not be too large. Considering comprehensively that 8 avalanche triodes are used in series to form a primary generator circuit in the design.When the generator stage n is 3, the output amplitude is about-6 kV, which has reached the output target. Considering that the output amplitude efficiency of the generator should be as large as possible and the half height width of the pulse should be as small as possible, a three-stage Marx pulse generator based on avalanche triode is used to realize nanosecond high-voltage pulse. The corresponding output pulse amplitude is-6.058 kV and full width at half maximum is 165.924 ns. A pulse shaping circuit is then designed based on the pulse steepening technology. The principle of pulse steepening is to rapidly charge and discharge small capacity capacitors through nanosecond pulses, shorten the pulse front time while losing part of the pulse amplitude, and shorten the pulse back time by reducing the trailing edge of the pulse. After steepening, the output pulse reaches picosecond. By analyzing the influence of circuit parameters on the picosecond gating pulse, the picosecond high-voltage gating pulse applied to the temporal resolution calculation of the microchannel plate framing camera is output, with an amplitude of-2.8 kV and a full width at half maximum of 124 ps. Monte Carlo method is used to establish the photoelectrons dynamic multiplication model in the MCP channel and the gating pulse is applied to the MCP gain calculation to obtain the temporal resolution. The process of obtaining the temporal resolution of the camera: first, the photoelectrons enter the MCP channel under the action of the gating pulse, and the photoelectrons collide with the MCP channel wall to generate secondary electrons;until the photoelectrons leave the MCP channel;finally, the MCP gain under the gating pulse at different times is calculated to obtain the temporal resolution of the MCP framing camera. The research results show that, the method of generating picosecond high voltage gating pulse by combining the Marx and the sharpening circuit is feasible. The gating pulse with an amplitude of-2.8 kV and a half-width of 124 ps is obtained when the Marx pulse generator is three stages, and the inductances and capacitance of the pulse sharpening circuit are 725 nH, 7 nH, and 1 pF respectively. The MCP gain time normalization curve with a half height width of about 53 ps is obtained by analyzing the dynamic multiplication process of photoelectrons in MCP channel at different times and calculating the gain, which is the temporal resolution of the MCP frame divider. In addition, since the waveform of the gating pulse is V-shaped, the pulse rising edge can be applied to the dilation gradient of pulse-dilation framing camera, which provides conditions for further improving the temporal resolution of pulse-dilation framing camera.
作者
崔逢祥
白雁力
伍思其
陈欢
梁禄业
朱云斐
谢军
CUI Fengxiang;BAI Yanli;WU Siqi;CHEN Huan;LIANG Luye;ZHU Yunfei;XIE Jun(School of Electronic Engineering and Automation,Guilin University of Electronic Technology,Guilin 541004,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2023年第1期232-239,共8页
Acta Photonica Sinica
基金
国家自然科学基金(No.11865007)
广西省自然科学基金(No.2022GXNSFAA035561)
广西自动检测技术与仪器重点实验室主任基金(No.YQ22101)
关键词
分幅相机
脉冲陡化技术
选通脉冲
蒙特卡洛法
时间分辨率
Framing camera
Pulse steepening technique
Gating pulse
The method of Monte Carlo
Temporal resolution
