光阴极注入器产生的高能电子束具有束长短、发射度低、亮度高、穿透能力适中等特点，以其作为探针进行成像有望实现同时具有微米级空间分辨和亚皮秒级时间分辨的高精度诊断。高能量密度物理条件下常同时包含物质密度和场的复杂变化，针对不同的目标特征，需利用不同的成像模式对特定信息进行诊断。本论文针对高能量密度物理中的磁场诊断提出了结合投影成像和透镜成像的诊断方法，并对其中的一些关键问题及应用进行了研究。 论文从束靶相互作用出发，研究了高能电子束基于弹性散射形成投影成像的机理，讨论了对电子束品质的要求。结合计算机仿真研究了束团聚焦尺寸及散角对成像空间分辨的影响，并针对静态样品开展了实验，获得了优于百微米的空间分辨。在此基础上开展了对于T·mm级强度磁场靶的诊断实验，根据成像结果反演得到了磁场分布，实验结果与预期相符，展示了成像诊断在刻画场强分布细节变化方面的独特优势，并为开展动态诊断实验打下基础。 论文对高能电子透镜成像中图像扭曲模糊的现象进行了深入研究，从理论和实验上揭示了其来源于磁透镜组中磁铁角度失配导致的电子x方向和y方向运动发生的耦合，并通过定义图像旋转角度和变形程度建立了评价指标。对成像系统关于磁铁角度失配敏感性的研究指出四单元四极透镜系统中需重点关注中间两块磁铁的角度失配程度，并给出了确定系统误差容忍度的方法。在此基础上提出了基于束斑形态的在线校准、选用更高的电子束能量和更大的放大倍数等措施来尽量降低磁铁角度失配对成像质量的影响。该研究方法对其他类似成像系统也同样适用，对于进一步提高成像质量具有重要意义。 在上述研究的基础上，论文针对高能量密度物理中磁场的诊断提出了结合投影成像和透镜成像的诊断方法。通过投影成像对磁场信息进行提取，进而利用透镜成像进行放大，可以实现对磁场精细结构的诊断。以金属丝电爆炸为诊断目标，完成了成像系统设计，其可行性在模拟研究中得到了较好的验证。设计并搭建了同步、诊断、监测系统，开展了初步的投影成像动态诊断实验，成功捕捉到金属丝放电不同时刻的图像，分析得到了金属丝附近亚T·mm量级积分强度磁场的分布，并测量得到爆炸产物膨胀速率为km/s量级，验证了诊断方法的可靠性。为下一步深入开展精细的物理诊断研究奠定了基础。
High energy electron beam generated by photocathode injector has short bunch length, high brightness, low emittance, and strong penetration ability. With the high quality beam, sub-ps time resolution as well as μm spatial resolution in high energy electron radiography are achievable. The mixture of mass and electromagnetic fields in high energy density physics (HEDP) brings difficulty in diagnosing. Thus different diagnostics are needed in different scenes. The shadow-lens radiography is proposed in this research for magnetic field diagnosis in HEDP and this dissertation is devoted to investigate the theoretical problems and applications of it. First, the imaging process of relativistic electron based on elastic scattering is analyzed, and the restrictions of beam parameters are given. Simulations are conducted to study the influence of beam size and divergence. Based on the analysis, experiments are carried out and spacial resolution better than 100 μm has been obtained. Furthermore, experiment results show that this method has great reliability in magnetic field diagnosing, and it performs well in capturing detail information in space distribution. Lens based high energy electron radiography are carried out and the image distortion caused by angular misalignment of quadrupole magnets are studied thoroughly. We propose that the distortion originates from the coupling of the motions of electron in transverse directions based on theoretical analysis via transfer matrix method. The relative angular rotation between the second and third magnetic quadrupoles in Russian Quatruplet system is identified to be the main contributor to image distortion, which is verified by both beam dynamics simulation and experimental outcomes. In addition, different strategies to mitigate this image distortion are explored, including magnets online tuning, using higher beam energy and larger magnification factor. This study provides some criteria for designing experiments, and paves the way to achieve higher image precision. The shadow-lens radiography is proposed to investigate low-intensity magnetic field. In this mode, the field information is extracted by shadowgraphy and then amplified by lens based radiography. The design of the imaging system of wire explosion has been conducted, and its feasibility has been proven in simulation. Besides, the synchronizing and diagnosing system has been constructed, and preliminary experiment of shadowgraphy diagnosing wire explosion has been carried out, which laid the fundation to further investigation.
