Fig. 2: Shot selection and summary statistics.
From: Observation of quantum effects on radiation reaction in strong fields
a The shot selection procedure is illustrated. Background-subtracted total counts measured by the gamma profile diagnostic are shown as a function of Q〈γ2〉 for all shots, where Q and γ denote electron beam total charge and Lorentz factor, respectively. A constant, Cγ = 1 × 105 has been added to the normalised total counts for all shots to allow the data to be shown on a logarithmic scale. Nulls (blue, 608 shots) consist of combined misses and beam-off shots. The latter lie within 1σ (cyan, dashed) of the scaling of background gamma yield with Q〈γ2〉 (cyan, continuous), where σ is the standard deviation of the fit to the background scaling. The small fraction of nulls that lie above this threshold are beam-off shots. Hits (red, 687 shots) lie 3σ (orange, dashed) above the background scaling. The grey points cannot be categorised as hits or nulls and thus are excluded from the analysis. The shots analysed using the Bayesian framework are encircled (black). b Simulated post-collision electron spectra, normalised by integration, predicted by different radiation reaction models for a collision between an electron beam (pre-collision spectrum shown) with a Gaussian temporal profile with full-width half-maxima (FWHM) 141 fs and a laser pulse with a0 = 14 and Gaussian transverse and longitudinal intensity profiles with FWHM 2.47 μm and 45 fs, respectively. The collision was offset temporally from the laser focus by 60 fs. The mean energy, 〈E〉, and peak height above the 70th percentile electron energy, P70, which indicates the prominence of the high-energy peak in the spectrum, are shown.
