RESUMEN
The photon beamline vacuum system of the European X-ray Free-Electron Laser Facility (European XFEL) is described. The ultra-large, in total more than 3â km-long, fan-like vacuum system, consisting of three photon beamlines is an essential part of the photon beam transport. It is located between the accelerator vacuum system and the scientific instruments. The main focus of the design was on the efficiency, reliability and robustness of the entire system to ensure the retention of beam properties and the operation of the X-ray optics and X-ray photon diagnostics components. Installation started in late 2014, the first of the three beamline vacuum systems was commissioned in spring 2017, and the last one was operational in mid-2018. The present state and experience from the first years of operation are outlined.
RESUMEN
The characteristic in-plane length scales of ultrathin films of regenerated cellulose are measured using noncontact atomic force microscopy (NC-AFM) and grazing incidence small-angle x-ray scattering (GISAXS) in ambient atmosphere and under various humidity conditions. The aim is to elucidate the structural basis for the excellent compatibility of cellulose supports to planar lipid membranes. Films are deposited on silicon wafers by Langmuir-Blodgett (LB) transfer and spin coating. NC-AFM height profiles and the resulting calculated power spectral density functions indicate that both kinds of cellulose films have almost identical root-mean-square roughness values (0.7-0.8 nm) and very similar characteristic length scales (32 nm), respectively. GISAXS measurements, both above and below the critical angle of total external reflection, show that the dominant length scales in the bulk and near the surface of the films are comparable ( approximately 50 nm). The origin of these length scales can be attributed to the bundle of rodlike molecules of cellulose that result during the regeneration process (i.e., as a consequence of the cleavage of the silyl side chains of trimethylsilylcellulose). Exposure of the cellulose samples to various humidities shows that above a relative humidity of 97% a significant swelling of the films occurs, which is consistent with our previous findings. The swelling of films with more than 30 LB monolayers of cellulose induces a remarkable out-of-plane rearrangement of the cellulose bundles, due to a reduced influence of the solid substrate compared to thinner films with only eight to ten LB monolayers.
RESUMEN
Highly oriented native cellulose fibres (flax) and softwood (pine) have been investigated by means of X-ray diffraction. Local structural information was obtained by using X-ray microbeams. Tensile tests were performed in situ, revealing a change of orientation of cellulose microfibrils in materials with tensile strain. In flax fibres, the microfibrils rotate during the first percent of stretching, into a more parallel orientation with respect to the fibre axis. For wood, a decrease of orientation with the onset of strain hardening is found for the first time.