Development, characterization and experimental performance of x-ray optics for the LCLS free-electron laser

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

“…This effect can be understood if one considers that the 1µm-thick B 4 C and SiC magnetron sputtered films that were used in these studies have lower densities (90-95% of bulk) and amorphous morphology 7 compared to their bulk counterparts, which are crystalline. Another general trend that can be seen in Figure 4 is that the damage thresholds for both bulk and thin film B 4 C and SiC materials are close to the theoretically predicted damage thresholds, which justifies the principles used for LCLS optics design and materials selection 2,3,6,7 . An important element to consider is the mechanisms that lead to damage in the photon energies of the FLASH vs. the LCLS FEL facilities.…”

“…B 4 C and SiC were chosen as the reflective coating materials for the LCLS soft x-ray and hard x-ray optics respectively, due to their predicted high damage thresholds against the LCLS FEL beam compared to other coating materials, combined with the good reflective performance and absence of electronic absorption edges in the 0.827-2 keV (for B 4 C in the soft x-ray) and 2 -24 keV (for SiC in the hard x-ray) energy ranges of operation. Our group at Lawrence Livermore National Laboratory (LLNL) has led a team composed of national laboratories and industry in the design, specification, fabrication, coating and precision surface metrology of all the x-ray mirrors installed at LCLS, and these topics are discussed in detail in earlier references 2,3,4,5,6,7 . The B 4 C and SiC coatings of the LCLS x-ray mirrors were developed at * e-mail: regina.soufli@llnl.gov, phone: 925-422-6013 LLNL and were deposited by DC-magnetron sputtering 8 on precisely figured and polished Si substrates supplied by commercial vendors.…”

Reliable before-fabrication forecasting of expected surface slope distributions for x-ray optics

“…[56][57][58] In this case, 1D PSD spectra of many high quality x-ray optics can be approximated by an inverse-power-law function Af  with a power parameter 1   . 57,74,75,80 For lower spatial frequencies, accessible for surface height measurements, for example, with large field-of-view Fizeau interferometers, the measured PSD spectra were found to be well approximated by an inverse-power-law function with a significantly larger power parameter, typically 2   . 57,74,75 This can occur as a result of normal polishing processes, where the surface starts out as a rough surface and then becomes smoother by knocking down the high frequency end of the spectrum faster than the low end.…”

Development, experimental performance and damage properties of x-ray optics for the LCLS free-electron laser

“…The CXI beamline also uses two pairs of focusing mirrors and the MEC beamline uses one flat steering mirror. In collaboration with other national laboratories and commercial vendors, Lawrence Livermore National Laboratory (LLNL) led the design, specification, mounting, precision surface metrology and modeling of several of the x-ray mirrors installed at LCLS, including all the x-ray mirrors in the FEE 2,3,4,5 .…”