Fig. 4.

Relativistic electron beam phase space and transported energy. a, b Relativistic electron beam (REB) transverse phase space (x, p_x) at the target’s rear surface, a without imposed B-field, b with imposed B-field. c Transported energy as a function of the propagation depth into the target, with (red) and without (blue) imposed B-field: total transported kinetic energy (W_k, diamonds) and its fraction within the initial REB radius r₀ centered on the target axis ($W_{\mathrm{k}-r_0}$, stars). All the plots correspond to the transport-target in configuration (ii), positioned at the coil plane