Fig. 1. Two sputter plates from fused silica are used to shield probe beam optics from debris in solid-target experiments at the ELI-NP high-power laser (HPL) facility. Note that the laser is focused to relativistic intensities via an off-axis parabola (OAP) onto a disk target, which is protected against debris by a thin pellicle. The front-side debris shield protects a polarizer aimed towards the target normal on the laser-interaction side of a disk target; the rear-side debris shield catches debris in front of an imaging lens. The target normal is collinear with the normal of both debris shields.

Fig. 2. Predicted transmittance through nickel deposit of thickness on a 1 mm thick silica plate for three channels of an RGB scan with the EPSON V-750-PRO flatbed scanner.

Fig. 3. Debris deposited on silica plates positioned in the target normal direction (a) atop the target rear, and (b) atop the target front side facing the high-power laser at the ELI-NP 1 PW facility. Elliptical dashed lines mark areas of a rough surface and the dashed squares indicate ROIs where the debris deposition is uniform. The silica plates are 50 mm squares; visible blank areas stem from mounting clamps used for positioning the plates.

Fig. 4. Detailed view on a mm-scale region in the vicinity of rough surface features (‘marks’) on the lens-sided sputter plate, using (a), (c) white-light interferometry and (b) a profilometer.

Fig. 5. Spectrally resolved transmittance of nickel debris illuminated with the light source in an EPSON V-750-PRO flatbed scanner; indicated are blue, green and red bands of acquisition for the scanner head. A measurement of intensities through silica glass is used to normalize the measurement through debris .

Fig. 6. Transmittance through the debris on the rear-side (with respect to the laser interaction) silica plate for all three channels of the RGB scan.

Fig. 7. Thickness of the nickel debris on the rear-side silica plate calculated from the transmittance separately for all three channels of the RGB scan.