Fig. 2

Integrated electron density measurements using the interferometer at 15 ps after the laser irradiation with and without applying the external magnetic field. Panels (a) and (b) show cases with and without an applied B-field (panel (a) is the same image as the one shown in Fig. 1c, just reported here for ease of comparison). Panel (c) plots longitudinal lineouts (at y = 0) for both cases (with B: solid black line, without B: dashed gray line), as well as the analytical calculation (dotted-dashed gray line) that corresponds to Supplementary Fig. 5d and that would result from a simple linear overlap of the two TNSA plasmas expanding from both targets. Note also that the without B-field case corresponds to Fig. 11 of ref. ²⁷. The calculation of the error bars is discussed at the end of the “Experiments” section of the Methods