Studies on the transport of high intensity laser-generated hot electrons in cone coupled wire targets

Abstract

Experimental results showing hot electron penetration into Cu wires using Kα fluorescence imaging are presented. A 500 J, 1 ps laser was focused at f/3 into hollow aluminum cones joined at their tip to Cu wires of diameters from 10 to 40 μm. Comparison of the axially diminishing absolute intensity of Cu Kα with modeling shows that the penetration of the electrons is consistent with one dimensional Ohmic potential limited transport. The laser coupling efficiency to electron energy within the wire is shown to be proportional to the cross sectional area of the wire, reaching 15% for 40 μm wires. Further, we find the hot electron temperature within the wire to be about 750 keV. The relevance of these data to cone coupled fast ignition is discussed.