Fig. 1

Schematic view of the snapshot retrieval method by Huang and colleagues. The method relies on the simultaneous measurement of optical transition radiation (OTR) through imaging and electro-optic sampling. Combined, these two diagnostics constrain the temporal and spatial structure of the electron bunch that generated the OTR. The 3D structure is then estimated by optimizing a multi-Gaussian distribution through an evolutionary search algorithm that matches the prediction from the model to the experimental data. Images adapted from [ref. ¹³]