Experimental observations of transport of picosecond laser generated electrons in a nail-like target

The transport of relativistic electrons, generated by the interaction of a high intensity (2 x 10(20) W/cm(2)) laser, has been studied in a nail-like target comprised of a 20 mu m diameter solid copper wire, coated with similar to 2 mu m of titanium, with an 80 mu m diameter hemispherical termination. A similar to 500 fs, similar to 200 J pulse of 1.053 mu m laser light produced by the Titan Laser at Lawrence Livermore National Laboratory was focused to a similar to 20 mu m diameter spot centered on the flat face of the hemisphere. K-alpha fluorescence from the Cu and Ti regions was imaged together with extreme ultraviolet (XUV) emission at 68 and 256 eV. Results showed a quasiexponential decline in K-alpha emission along the wire over a distance of a few hundred microns from the laser focus, consistent with bulk Ohmic inhibition of the relativistic electron transport. Weaker K-alpha and XUV emission on a longer scale length showed limb brightening suggesting a transition to enhanced transport at the surface of the wire. (C) 2007 American Institute of Physics.