Development of High Fluence X-Ray Sources Using Laser Heated Novel Nano-Wire Metal Foams

Abstract

High fluence K-shell and L-shell x-ray sources are desired for various high energy density physics experiments. One efficient method for creating such a source is the laser heating of materials that are underdense to laser light. Nano-wire foams are an ideal choice for an underdense material and have average densities of 6-15 mg/cm 3 . The manufacture of robust Cu, Ag and Au nano-wire foams into millimeter scale targets is possible through a technique of freeze casting an aqueous suspension of nano-wires. Cylindrical targets with sizes between 2 to 4 mm have been shot on both the NIF and the Omega laser facilities. For example, x-ray conversion efficiencies (XRCE) from silver nano-wire foams have been measured to be ~1.0% when heated with ~400 TW of 3w laser light in a 2.5 ns square pulse from the NIF laser system. The XRCE from foam targets have been found to be ~2 times that observed in metal lined cylindrical cavity targets and ~5 times that observed in prepulsed metal foils. Experimental results and comparisons with simulations will be presented.