Fig. 1. Schematic of an XFEL beam incident on a B₄C/Si-sub mirror under grazing incidence.

Fig. 2. Absorbed energy fractions along the depth direction for B₄C(50 nm)/Si-sub irradiated by XFEL at 1 keV and 12 keV with the grazing incidence angle of 2 mrad.

Fig. 3. Time-dependent depth distribution of enthalpy for B₄C(50 nm)/Si-sub irradiated by XFEL at the fluence of (a) 1250 J/cm² at 1 keV and (b) 2.4 × 10⁵ J/cm² at 12 keV. The grazing incidence angle is 2 mrad in both cases. The interface between B₄C and Si-sub is marked by dashed gray lines, and the damage boundary is marked by solid white curves.

Fig. 4. Absorbed energy fraction for B₄C/Si-sub mirror with different B₄C film thicknesses at the photon energy of 12 keV and the grazing incidence angle of 2 mrad.

Fig. 5. Damage thresholds of B₄C mirrors with different B₄C film thicknesses (solid black squares) at 12 keV and the grazing angle of 2 mrad; reflectivity of B₄C mirrors as a function of film thickness calculated with IMD software (blue line).

Fig. 6. Damage threshold of the B₄C(50 nm)/Si-sub mirror at different X-ray energies (solid blue squares). The theoretical reflectivity was calculated using IMD software (solid red line). The absorption K-edge of Si at 1.839 keV is indicated by a green dashed line.