Wavelength dependence of the damage threshold of inorganic materials under extreme-ultraviolet free-electron-laser irradiation

Abstract

We exposed bulk SiC and films of SiC and B4C to single 25 fs long free-electron-laser pulses with wavelengths between 13.5 and 32 nm. The materials are candidates for x-ray free-electron laser optics. We found that the threshold for surface-damage of the bulk SiC samples exceeds the fluence required for thermal melting at all wavelengths. The damage threshold of the film sample shows a strong wavelength dependence. For wavelengths of 13.5 and 21.7 nm, the damage threshold is equal to or exceeds the melting threshold, whereas at 32 nm the damage threshold falls below the melting threshold.

Interaction of short x-ray pulses with low-Z x-ray optics materials at the LCLS free-electron laser

“…We find a slightly lower damage threshold for multiple pulses. Similar to the trends observed in experiments at longer wavelengths [2], the damage threshold is somewhat higher for bulk materials than for thin (µm-thick) films. Unlike in the longer-wavelength experiments, we observed strong mechanical cracking in the materials, which may be due to the larger penetration depths of the hard x-rays.…”

“…We now compare the damage behavior observed on similar materials at lower photon energies at FLASH [2,3] with the present LCLS results. In both cases, we observed that the damage thresholds of bulk materials are somewhat above the melt threshold, whereas the damage threshold for films is below.…”

“…At the same time, their unique output characteristics put severe requirements on the optics used to guide and shape the x-ray pulses and the detectors used to characterize them. This involves a new regime of radiation-matter interaction, which has been investigated in a series of experiments at the free electron laser in Hamburg (FLASH) at photon energies up to 177 eV [2][3][4]. The extreme ultraviolet (EUV) radiation available at FLASH interacts primarily with valence shell electrons and the penetration depth is much smaller than the beam diameter.…”

Ultrafast self-gating Bragg diffraction of exploding nanocrystals in an X-ray laser

“…At longer time scales, processes not included in the present model would have to be considered, such as vaporization [48], ablation in bulk solids (on nanoseconds time scales) [53][54][55] and even resolidification (100 ns time scales) [56].…”

Lifetime and damage threshold properties of reflective x-ray coatings for the LCLS free-electron laser

“…To determine the experimental damage thresholds of B 4 C and SiC materials, several experiments spanning the photon energy range from 38.7 eV to 830 eV (32 nm to 1.5 nm) have been performed at the LCLS and FLASH FEL facilities 15,16 . The results are summarized in Figure 4 below.…”