Proton scattering at grazing angles. (top left) Schematic view of the simulation setup, showing the proton beam exiting the collimator and scattered by the mirror sample towards the detector. Measured, in red, and simulated, in black, proton scattering efficiency at 300 keV for three grazing incident angles, 0.5° (top right), 0.64° (bottom left), and 0.81° (bottom right), hitting the eROSITA mirror sample. The simulation error bars are the sum of the 1σ statistical and systematic uncertainties.