Study of the influence of various pre-plasma conditions on laser-proton acceleration via x-ray spectroscopy

Laser driven ion acceleration is a fast growing field, where understanding of the internal processes of laser-plasma interaction is crucial for optimization of such ion sources. Namely, x-ray spectroscopy offers a unique in-situ view at plasma conditions and electron signatures from within the target, which can help to identify important parameters for optimization of the laser-driven acceleration process.

Here, we present an x-ray spectroscopy platform installed at the Draco PW laser facility (Ti:sapphire 30 fs laser system) and how the addition of x-ray spectroscopy reveals the suprathermal electron population, which provides insight into the energy conversion from laser to the proton-accelerating sheath.

As an example, we study the impact of pre-plasma tailoring on characteristic x-ray emission and proton acceleration via controlled introduction of various pre-pulses on the Ti 2 μm thick target that precede the arrival of the main laser pulse by 2.5 − 30 ps. Based on our data from x-ray spectroscopy combined with proton diagnostics we then gain understanding of the underlying processes in proton acceleration and the influence of pre-plasma formation.