 | \it \small a) Electron bunch imaged onto the spectrometer screen after propagation through vacuum. b) Electron bunch imaged onto the spectrometer screen after propagation through $10\,$ meters of plasma. The horizontal axis is the dispersive plane. The counts of each image are normalized to the respective maximum. c) and d) show a waterfall plot of the energy projections of the electron beam imaged on the spectrometer screen. c) 30 events with the smallest beam size at the plasma entrance; d) 30 events with the largest beam size at the plasma entrance. e) sums of the energy distributions for the two cases: (c) in blue and (d) in orange. For all images, the electron bunch charge at the plasma entrance is $150\,$pC and the energy is $\sim18.5\,$MeV. |