Double in-line plasma-mirror-based contrast enhanced laser-ion acceleration at the Centre for Advanced Laser Applications

Temporal laser contrast plays a vital role in laser-based fusion concepts, as for example the one recently proposed by Marvel Fusion (Ruhl and Korn, arXiv:2202.03170v5, 2022). We have demonstrated for the first time an in-line Double Plasma Mirror (DPM) setup at the Laser-driven ION (LION) beamline of the Centre for Advanced Laser Applications (CALA). This set-up yielded significant enhancement in laser contrast with as little as 20% losses.

Reflectance measurements yielded a contrast enhancement of 10^2 and 10^4 for uncoated and AR-coated substrates, respectively. We investigated the maximum kinetic proton energy, transverse proton beam profiles and laser-to-ion conversion efficiency.

Without plasma mirrors the maximum achieved kinetic proton energies along target normal diminished with decreasing target thickness observing no protons when irradiating 10 nm thin foils. The addition of plasma mirrors yielded increased particle numbers and a proton signal for the entire range of target thicknesses. With uncoated substrates, kinetic proton energies peaked at a target thickness of 25 nm. With coated substrates we see increasing kinetic energies towards thinner targets.