A single-shot measurement of electron emittance was experimentally accomplished using a focused transfer line with a dipole. The betatron phase of electrons based on laser wakefield acceleration (LWFA) is energy dependent owing to the coupling of the longitudinal acceleration field and the transverse focusing (defocusing) field in the bubble. The phase space presents slice information after phase compensation relative to the center energy. Fitting the transverse size of the electron beam at different energy slices in the energy spectrum measured 0.27 mm mrad in the experiment. The diagnosis of slice emittance facilitates local electron quality manipulation, which is important for the development of LWFA-based free electron lasers. The quasi-3D particle-in-cell simulations matched the experimental results and analysis well.

高能同步辐射光源的增强器将直线加速器注入的束流加速到储存环所需的能量，为储存环提供高品质的电子束。为了对增强器的束流横向截面尺寸、发射度及能散进行测量，设计了两条可见光-紫外波段的束测光束线。两条光束线分别选取无色散和色散较大的两处弯铁位置作为光源点，使用两套同步光成像系统来监测光源点的束流截面尺寸，并计算束流发射度及能散。介绍了同步光引出真空室及光学成像系统，对影响成像质量的空间分辨率进行了分析，并针对升能过程中不同能量下束流光斑变化的测量进行了设计。