Full aperture backscatter diagnostics for characterization of laser plasma instabilities at the extreme light infrastructure (ELI) beamlines

We report on the commissioning of a full aperture backscatter diagnostics station for the kilojoule, nanosecond high repetition rate L4n laser operating at a wavelength of 527 nm at the Extreme Light Infrastructure (ELI) - Beamlines, Dolni Brezany, Czech Republic. Light scattered back from laser-plasma interaction into the cone of the final focusing lens is captured and split into different channels to measure the signatures of laser plasma instabilities from stimulated Brillouin scattering, stimulated Raman scattering, and two plasmon decay with respect to back scattered energy, its spectrum, and its temporal profile. The performance was confirmed in a commissioning experiment with more than 800 shots at laser intensities ranging from 0.5 × 1013 to 1.1 × 1015 W cm-2. These diagnostics are permanently installed at ELI Beamlines, and can be used to understand the details of laser-plasma interactions in experiments with kJ and 527 nm light. The large number of shots that can be collected in an experimental campaign will allow us to study the details of the laser-plasma interaction with a high level of confidence.

Monitoring of the heavy-ion beam distribution using poly- and monochromatic x-ray fluorescence imaging

In this work, the first proof of the principal of an in situ diagnostics of the heavy-ion beam intensity distribution in irradiation of solid targets is proposed. In this scheme, x-ray fluorescence that occurs in the interaction of heavy-ions with target atoms is used for imaging purposes. The x-ray conversion to optical radiation and a transport-system was developed, and its first test was performed in experiments at the Universal Linear Accelerator in Darmstadt, Germany. The Au-beam intensity distribution on thin foils and Cu-mesh targets was imaged using multiple x-ray pinholes (polychromatic imaging) and 2D monochromatic imaging of Cu K_α radiation by using a toroidally bent silicon crystal. The presented results are of importance for application in experiments on the investigation of the equation of states of high energy density matter using high intensity GeV/u heavy-ion beams of ≥10¹⁰ particles/100 ns.