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%.