Microstructured layered targets for improved laser-induced x-ray backlighters

We present the usage of two-layer targets with laser-illuminated front-side microstructures for x-ray back lighter applications. The targets consisted of a silicon front layer and copper back side layer. The structured layer was irradiated by the 500-fs PHELIX laser with an intensity above 1020 W cm(-2). The total emission and one-dimensional extent of the copper K alpha x-ray emission as well as a wide spectral range between 7.9 and 9.0 keV were recorded with an array of crystal spectrometers. The measurements show that the front-side modifications of the silicon in the form of conical microstructures maintain the same peak brightness of the K alpha emission as flat copper foils while suppressing the thermal emission background significantly. The observed K alpha source sizes can be influenced by tilting the conical microstructures with respect to the laser axis. Overall, the recorded copper K alpha photon yields were in the range of 10(11) sr(-1), demonstrating the suitability of these targets for probing applications without subjecting the probed material to additional heating from thermal line emission.