Figure 2
From: Shock assisted ionization injection in laser-plasma accelerators

Angularly resolved electron spectra of ten consecutive shots, with a shock front and a gas mixture (a) or pure helium (b). The electron density at the center of the density profile is 4 ± 0.1 × 1018 cm−3 in (a) and 3 ± 0.1 × 1018 cm−3 in (b). The shock front is located 1.03 ± 0.02 mm from the center of the density profile in (a) and 1.34 ± 0.02 mm in (b). The small differences in density and shock front position explain the difference in the electron beam energy between (a,b). The spectra are corrected from the spectrometer dispersion. The color bar goes from 0 (blue) to 83000 electrons per MeV per mrad (red). (c,d) Corresponding mean electron spectra, with standard deviation in colored area.