Wideband multilayer mirrors with minimal layer thicknesses variation

Wideband multilayers designed for various applications in hard X-ray to Extreme UV spectral regions are based on a layered system with layer thicknesses varying largely in depth. However, because the internal structure of a thin film depends on its thickness, this will result in multilayers in which material properties such as density, crystallinity, dielectric constant and effective thickness vary from layer to layer. This variation causes the fabricated multilayers to deviate from the model and negatively influences the reflectivity of the multilayers. In this work we solve this problem by developing designs of wideband multilayers with strongly reduced layer thickness variations in depth, without essential degradation of their optical characteristics

Narrow-band Borrmann multilayer filters for monitoring of EUV sources

EUV sources currently under development for high volume manufacturing are based on hot plasmas that produce next to 13.5 nm also broadband blackbody radiation and out-of-band line emissions.\ud For the accurate monitoring of the in-band (13.5 nm ± 2%) radiation power, narrow-band-pass filters are required. Standard filters such as absorptive thin layers can provide neither very narrow bandwidths, nor wavelength selectivity.\ud We propose an approach based on the Borrmann effect applied to multilayer stacks. This effect relies on the matching of the standing wave field within the multilayer stack with the structure: the minima of the wave field intensity are placed in the center of the absorbing layers, resulting in a resonant decrease in absorption and a narrow-band transmission spectrum for a specific wavelength.\ud We show calculated transmission spectra of Borrmann filters optimized for different bilayer materials, bandwidths, transmissions and wavelengths

Growth of nano dots on the grazing incidence mirror surface under FEL irradiation Analytic approach to modeling

Simple analytic equation is deduced to explain new physical phenomenon detected experimentally growth of nano dots 40 55 nm diameter, 8 13 nm height, 9.4 dots amp; 956;m2 surface density on the grazing incidence mirror surface under the three years irradiation by the free electron laser FLASH 5 45 nm wavelength, 3 degrees grazing incidence angle . The growth model is based on the assumption that the growth of nano dots is caused by polymerization of incoming hydrocarbon molecules under the action of incident photons directly or photoelectrons knocked out from a mirror surface. The key feature of our approach consists in that we take into account the radiation intensity variation nearby a mirror surface in an explicit form, because the polymerization probability is proportional to it. We demonstrate that the simple analytic approach allows to explain all phenomena observed in experiment and to predict new effects. In particular, we show that the nano dots growth depends crucially on the grazing angle of incoming beam and its intensity growth of nano dots is observed in the limited from above and below intervals of the grazing angle and the radiation intensity. Decrease in the grazing angle by 1 degree only from 3 to 2 degree may result in a strong suppression of nanodots growth and their total disappearing. Similarly, decrease in the radiation intensity by several times replacement of free electron laser by synchrotron results also in disappearing of nano dots growt

Effect of the surface roughness on X ray absorption by mirrors operating at extremely small grazing angles

This study theoretically analyzes an increase in X ray absorption by a grazing incidence mirror due to its surface roughness. We demonstrate that the increase in absorption can be several hundred times larger than predicted by the Nevot Croce formula. As a result, absorption enhances by several times compared to a perfectly smooth mirror despite the extremely small grazing angle of an incident X ray beam a fraction of the critical angle of the total external reflection and the high quality of the reflecting surface the roughness height was 0.5 nm in modeling . The main contribution to the absorption increase was dictated by the mid scale roughness waviness of the virgin substrate surface, whose quality thus defines an absorption enhancement. The approach was applied to the analysis of two real mirrors used in a synchrotron BESSY I and a European X ray free electron laser XFEL beamline. The modern surface finishing technology of elastic emission machining provides extremely low substrate waviness, guaranteeing the negligible effect of the surface roughness on the absorption increas

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II) as a precursor instead of Fe(III). This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III) oxide impurities which are detrimental for the process selectivity. The system containing Fe(II) and Mo(VI) species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II)–Mo(VI) system: (i) formation of complexes between Fe(II) and molybdate(VI) ions, (ii) inner sphere oxidation of coordinated Fe(II) by Mo(VI) and (iii) decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III) molybdate, Mo(VI) hydrous trioxide and molybdenum blue. Solid molybdoferrate(II) prepared by interaction of Fe(II) and Mo(VI) in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II) precursor was tested in methanol-toformaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III)