空间电荷效应对时间展宽分幅变像管时空性能的影响

摘要

X射线分幅相机是惯性约束聚变实验中的重要二维超快诊断设备,具有长漂移区结构的时间展宽分幅相机,在大幅度提升时间分辨性能的同时,会使空间电荷效应时空弥散变大.为探讨空间电荷效应的影响,以短磁聚焦分幅变像管为例,通过平均场模型和电子轨迹及成像分布研究空间电荷效应的时空弥散,并分析其对像管的影响.研究和分析结果表明,空间电荷效应引起的时间弥散与阴极电压、展宽脉冲斜率和漂移距离有关,空间弥散与成像系统和电子脉冲电流密度相关.当分幅变像管的时间分辨率提升至2 ps左右时,空间电荷效应的时间弥散相当于物理时间分辨,成为制约时间分辨性能进一步提升的主要因素,此时像管空间分辨性能降低8 % 左右.通过对像管空间电荷效应研究及其降低方法的探讨,为亚皮秒时间分辨分幅变像管的研制提供理论参考.%X-Ray framing cameras are an important two-dimensional ultrafast diagnostic tool in inertial confined fusion experiments.Although the temporal performance of framing cameras is further im-proved by the long drift area,the space charge effect(SCE)is increased as well.In order to study the influence of SCE on the framing tube,similar to the magnetic focused framing tube,for example,the temporal dispersion and spatial dispersion of SCE are studied using the mean field model,electron trajectory,and imaging distribution,and the influence of SCE on the framing tube is analyzed.The results of study and analysis show that the temporal dispersion is related to the cathode bias,dilated pulse,and drift distance,and the spatial dispersion is related to the imaging system and electron den-sity.When the temporal resolution is improved to ~2 ps,further increase of temporal resolution is restricted by the temporal dispersion,w hich is a major factor and close to physical temporal;the spa-tial resolution is decreased to ~8 %.A theoretical reference for the sub-picosecond framing tube is provided by studies on SCE and methods of its reduction.