Enhanced brightness of a laser-driven X-ray and particle source by microstructured surfaces of silicon targets

The production of intense X-ray and particle sources is one of the most remarkable aspects of high energy laser interaction with a solid target. Wide application of these laser-driven secondary sources require a high yield which is partially limited by the amount of laser energy absorbed by the target. Here, we report on the enhancement of laser absorption and X-ray and particle flux by target surface modifications. In comparison to targets with flat front surfaces our experiments show exceptional laser-to-target performance for our novel coneshaped silicon microstructures. The structures are manufactured via laser-induced surface structuring. Spectral and spatial studies of reflectance and X-ray generation reveal significant increases of the silicon Kα line as well as a boost of the overall X-ray intensity, while the amount of reflected light decreases. Also, the proton and electron yield is enhanced, but both temperatures stay comparable to flat foil targets. We support the experimental findings with 2D PIC simulations to identify the mechanisms responsible for the strong enhancement. Our results demonstrate how custom surface structures can be used to engineer high power laser-plasma sources for future applications.