The effect of target material on fast-electron transport is investigated using a high-intensity (0.7 ps, ${10}^{20}\mathrm{W}/{\mathrm{cm}}^2$) laser pulse irradiated on multilayered solid Al targets with embedded transport (Au, Mo, Al) and tracer (Cu) layers, backed with millimeter-thick carbon foils to minimize refluxing. We consistently observed a more collimated electron beam (36% average reduction in fast-electron induced Cu $K\alpha$ spot size) using a high- or mid-$Z$ (Au or Mo) layer compared to Al. All targets showed a similar electron flux level in the central spot of the beam. Two-dimensional collisional particle-in-cell simulations showed formation of strong self-generated resistive magnetic fields in targets with a high-$Z$ transport layer that suppressed the fast-electron beam divergence; the consequent magnetic channels guided the fast electrons to a smaller spot, in good agreement with experiments. These findings indicate that fast-electron transport can be controlled by self-generated resistive magnetic fields and may have important implications to fast ignition.

• Received 27 July 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.025001