Fig. 2: Recovery time of a beam-driven plasma wake.
a, The energy spectra and transverse distributions of the probe bunches after interaction with an unperturbed plasma. b, The same as in a but after interaction with a plasma perturbed by the leading bunch. Imperfections in the procedure used to subtract the overlapping spectra of the leading bunch from the driving probe bunch (Methods) lead to small systematic differences between the energy spectra of a and b at late timescales, for example, in the large betatron-mismatch band at approximately 1,030 MeV. Larger trailing-probe-bunch charge is also seen in b at shorter timescales due to higher coupling between the plasma and downstream capturing optics. c, The residuals (Methods) between the energy spectra and transverse bunch size of both the unperturbed and perturbed datasets. Extended data up to 160 ns is shown on a compressed horizontal timescale in the right-hand panel. The error bar represents the standard error of the mean. The recovery time, indicated by the black dashed vertical line, is reached when all three residuals are consistent with zero. The three experimental signatures of ion motion are enumerated in b, with orange dashed bands for the first signature added to a and b to guide the eye.
