脉冲展宽分幅相机的磁聚焦时间弥散和畸变
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摘要
模拟相机磁场分布和光电子运动轨迹,建立传输时间和距离的二维分布模型,分析磁聚焦时间弥散和畸变的成因及其降低方法。研究结果表明,时间弥散和畸变与物点(即阴极位置)沿轴磁场强度密切相关,并随物点离轴距离的增大而变大,通过适当提升轴对称磁场均匀性可降低磁聚焦时间弥散和畸变。当漏磁缝隙由4 mm扩宽至40 mm时,轴上与离轴30 mm物点的沿轴磁场强度峰值比由0.82提高到0.89,时间弥散由127 fs和435 fs分别减小至120.6 fs和378.4 fs,离轴30 mm物点的时间畸变率由4.61%下降至4.01%。
The magnetic field distributions and photoelectron trajectories of the camera are simulated, the two-dimensional distribution model of the transmission time and distance are built, and the causes and reduction methods for the magnetic focusing temporal dispersion and distortion are analyzed. The research results show that, the temporal dispersion and distortion are closely related to the magnetic field intensity along the axis of object point(cathode position), which increase with the increase of the off-axis distance of object point indicating that the magnetic focusing temporal dispersion and distortion can be reduced by the improvement of the uniformity of the axisymmetric magnetic field. As the gap of the magnetic leakage broadens from 4 mm to 40 mm, the peak value ratio between the on-axis magnetic field intensity and the 30 mm off-axis one increases from 0.82 to 0.89. Simultaneously, the temporal dispersion is reduced from 127 fs and 435 fs to 120.6 fs and 378.4 fs, respectively, and the temporal distortion for 30 mm off-axis decreases from 4.61% to 4.01%.
The magnetic field distributions and photoelectron trajectories of the camera are simulated, the two-dimensional distribution model of the transmission time and distance are built, and the causes and reduction methods for the magnetic focusing temporal dispersion and distortion are analyzed. The research results show that, the temporal dispersion and distortion are closely related to the magnetic field intensity along the axis of object point(cathode position), which increase with the increase of the off-axis distance of object point indicating that the magnetic focusing temporal dispersion and distortion can be reduced by the improvement of the uniformity of the axisymmetric magnetic field. As the gap of the magnetic leakage broadens from 4 mm to 40 mm, the peak value ratio between the on-axis magnetic field intensity and the 30 mm off-axis one increases from 0.82 to 0.89. Simultaneously, the temporal dispersion is reduced from 127 fs and 435 fs to 120.6 fs and 378.4 fs, respectively, and the temporal distortion for 30 mm off-axis decreases from 4.61% to 4.01%.
引文
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[3] Cai H Z,Liu J Y,Fu W Y,et al.Measurement technology of time of flight based on gated microchannel plates[J].Acta Optica Sinica,2018,38(2):0204002.蔡厚智,刘进元,付文勇,等.基于微通道板选通的飞行时间测量技术[J].光学学报,2018,38(2):0204002.
[4] Cai H Z,Liu J Y,Fu W Y,et al.Gated framing camera with three channels and its trigger jitter measurement[J].Acta Optica Sinica,2018,38(2):0204001.蔡厚智,刘进元,付文勇,等.三通道门控分幅相机及其触发晃动测量[J].光学学报,2018,38(2):0204001.
[5] Hilsabeck T J,Hares J D,Kilkenny J D,et al.Pulse-dilation enhanced gated optical imager with 5 ps resolution[J].Review of Scientific Instruments,2010,81(10):10E317.
[6] Nagel S R,Hilsabeck T J,Bell P M,et al.Dilation X-ray imager a new/faster gated X-ray imager for the NIF[J].Review of Scientific Instruments,2012,83(10):10E116.
[7] Nagel S R,Hilsabeck T J,Bell P M,et al.Investigating high speed phenomena in laser plasma interactions using dilation X-ray imager (invited)[J].Review of Scientific Instruments,2014,85(11):11E504.
[8] Bai Y L,Long J H,Liu J Y,et al.Demonstration of 11-ps exposure time of a framing camera using pulse-dilation technology and a magnetic lens[J].Optical Engineering,2015,54(12):124103.
[9] Cai H Z,Zhao X,Liu J Y,et al.Dilation framing camera with 4 ps resolution[J].APL Photonics,2016,1(1):016101.
[10] Nagel S R,Benedetti L R,Bradley D K,et al.Comparison of implosion core metrics:a 10 ps dilation X-ray imager vs a 100 ps gated microchannel plate[J].Review of Scientific Instruments,2016,87(11):11E311.
[11] Nagel S R,Chen H,Park J,et al.Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation[J].Applied Physics Letters,2017,110(14):144102.
[12] Cai H Z,Fu W Y,Bai Y L,et al.Simulation of a dilation X-ray framing camera[J].Journal of Electronic Imaging,2017,26(4):043003.
[13] Bradley D K,Bell P M,Landen O L,et al.Development and characterization of a pair of 30-40 ps X-ray framing cameras[J].Review of Scientific Instruments,1995,66(1):716-718.
[14] Izumi N,Hall G N,Carpenter A C,et al.Development of a dual MCP framing camera for high energy X-rays[J].Review of Scientific Instruments,2014,85(11):11D623.
[15] Naser B A.Design of free-distortion and rotation magnetic lens[J].Journal of Babylon University/Pure and Applied Sciences,2014,22(9):2525-2529.
[16] Chen J Y,Cai H Z,Bai Y L,et al.Imaging distortion analysis and testingof short magnetic focusing image converter tube[J].Laser & Optoelectronics Progress,2018,55(3):031101.陈家堉,蔡厚智,白雁力,等.短磁聚焦变像管的成像畸变分析与测试[J].激光与光电子学进展,2018,55(3):031101.
[17] Kasper E.An advanced boundary element method for the calculation of magnetic lenses[J].Nuclear Instruments and Methods in Physics Research Section A,2000,450(1):173-178.
[18] Bai Y L,Long J H,Cai H Z,et al.Influence of double magnetic lenses on performance of pulse-dilation framing tube[J].Laser & Optoelectronics Progress,2016,53(1):013201.白雁力,龙井华,蔡厚智,等.双磁透镜对时间展宽分幅变像管性能的影响[J].激光与光电子学进展,2016,53(1):013201.
[19] Liu R,Tian J S,Li H,et al.Design and evaluation of a pre-traveling wave deflector magnetic solenoid lens focused streak image tube[J].Acta Physica Sinica,2014,63(5):058501.刘蓉,田进寿,李昊,等.行波偏转器前置短磁聚焦条纹变像管理论设计与实验研究[J].物理学报,2014,63(5):058501.