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Final Report Summary - 3D RZP (The advanced instrumentation on the basis of 3D RZP for modern UV and X-ray sources)

The most important, in terms of understanding the nature of physical phenomena, experiments require time resolution on the scale of femto- (10-15) and atto (10-18)-seconds. The scope of physical phenomena under investigation with pulsed radiation is very wide, including the understanding of chemical dynamics when the timescales of nuclear and electronic motion can coincide, femtosecond movies of a chemical reaction, ultrafast dissociation investigations, and spin dynamics investigations. The next-generation light sources as e.g. energy-recovery linear accelerators (ERLs), free electron lasers (FELs), and high harmonic generators (HHGs) are opening new possibilities in research, due to their large peak power and short pulses. The availability of suitable diffractive optics preserving the temporal length is the basis of further progress in measurement techniques.
The 2-dimensional and 3-dimensional diffractive optical elements (DOEs), based on total external reflection, give the unique possibility for spectroscopy and focusing in application to 3rd, 4th and 5th generation light sources. Such DOEs are based on the principle of energy dispersion in the focal plane of a Reflection Fresnel Zone Plate (RZP). In the frame of present Marie Curie project, we focused on the elaboration of novel approaches for design and fabrication of 2D and 3D DOEs working in the entire energy range, from THz to hard X-rays. These optical elements have unique combination of properties and can operate at all XUV sources including FELs and HHGs. We fabricated 2D and 3D DOEs for time-resolved spectroscopy (energy range 410 – 1900 eV, 7500-9500 eV), FELs and ERLs (energy range up to 3 keV), and HHGs (energy range 10 – 200 eV). Such 2D and 3D DOEs are able to cover the energy range of up to 20 keV, and presently are not available somewhere else in the world.
The constructed Femtoslicing facility at BESSY-II is the only storage-ring-based facility yielding soft X-ray pulses of ~100 fs duration and variable polarization. Slicing facilities inherently generate intrinsic synchronization of femtosecond X-ray and femtosecond laser pulses, which is the most salient advantage of storage-ring-based slicing compared with similar experiments at FELs. However, the extraordinary temporal stability of storage-ring-based sources of ultrashort X-ray pulses is only possible at the expense of photon flux. To compensate this disadvantage, we have successfully designed, built and commissioned a novel type of high-flux Femtoslicing beamline for ultrafast applications. This unique set-up is based on the use of optical scheme with one optical element (off-axis RZP). Therefore, the constructed slicing beamline exhibits at least 20 times higher efficiency. We developed a unique novel approach: array of off-axis RZPs (RZPAs) that covers a large bandwidth. The current design consists of nine 2D RZPs that enable a working range from 410 to 1333 eV at resolutions of E/ΔE=500 or E/ΔE=2000. The beamline went into user operation in 2012 and has been proven to perform a new class of ultrafast applications with variable optical excitation wavelength and variable polarization. Therefore, we designed and fabricated the next generation of RZPAs: 3D RZPA with individual profile depths for each specific lens to further gain the flux up to further 20% what is significant for such photon-eating experiments. Eleven lenses, designed for the energies of 410 eV, 543 eV, 644 eV, 713 eV, 786 eV, 861 eV, 1083 eV, 1190 eV, 1293 eV, 1409 eV and 1900 eV which correspond to N-K, O-K, Mn-L, Fe-L, Co-L, Ni-L, Sm-M, Gd-M, Dy-M and Er-M absorption edges have been fabricated.
Using our 2D and 3D DOEs, the unique approach to biological time-resolved L-edge X-ray absorption spectroscopy at free electron lasers with high-transmission energy-discriminating spectrometer was developed. Such DOEs were optimized for discrimination of Mn L- and O K-fluorescence at 640 eV with bandwidth 20 eV. The spectrometer consists of 3-100 RZPs on a single Si substrate. Based on theoretical estimations, the DOE with a 3D depth profiling along an optical axis from 10 to 22 nm has been fabricated. This improvement allowed increasing the DOE efficiency in 1.2 times compare to the 2D DOE. Our concept provides a solid angle larger up to order of magnitude compared to more conventional high-resolution X-ray spectrometers with grazing-incidence gratings in Rowland geometry. We expect that this approach will be suitable for collecting XAS of dilute solvated species in the mM range efficiently at FELs, will enable to gain insights into the chemical interactions of 3d transition metal catalysts in metalloenzymes and biomolecules, and to pave the way for their investigation with time-resolved L-edge spectroscopy at FELs.
The existing microfabrication technology, including e-beam lithography, photolithography, plasma-chemical etching (PCE), and vacuum coating has been revised and modified with respect to accuracy, uniformity, and reproducibility of such DOEs. Process of precise Si PCE with variable along surface depth profile has been developed for the first time during this project. We elaborated a revolutionary approach for DOE, based on the application of milling ion etching for profiling of DOE fine structures with lateral periods down to 100 nm. Using this approach, a new generation of high-precision plasma-milling instrumentation has been developed and constructed. Its ion source allows uniform etching with reproducible low etching rate 1 nm/min. The advantage of such ion source is combined with scanning of the sample with a precision of 1 μm. We demonstrated possibility for the diffractive structure fabrication with a depth profile 4-30 nm with lateral periods <100 nm. The uniformity and reproducibility of the depth structure vary by less than 0.5 nm within the area of 80x80 mm2. We obtained characteristics are state-of-the-art and not available among the scientific community nowadays.

Marie-Curie Fellow:
Dr. habil. Maria Brzhezinskaya
Helmholtz-Zentrum Berlin fuer Materialien und Energie
Albert-Einstein-Str. 15
12489 Berlin, Germany
Phone +49-30-8062-14915
Fax +49-30-8062-12990

Scientist in charge:
Prof. Dr. Alexei Erko
Helmholtz-Zentrum Berlin fuer Materialien und Energie
Albert-Einstein-Str. 15
12489 Berlin, Germany
Phone +49-30-8062-12945
Fax +49-30-8062-12990

Informations connexes


Yvonne Tomm, (Head of Department)
Tél.: +49 30 8062 13643
Numéro d'enregistrement: 183766 / Dernière mise à jour le: 2016-06-06
Source d'information: SESAM