Polycapillary-boosted instrument performance in the extreme ultraviolet regime for inverse photoemission spectroscopy

A collimating polycapillary half lens, traditionally used in the medium and hard X-ray band, is operated at a photon energy of 36 eV for the first time. While the transmission still exceeds 50%, the measured and simulated spatial resolution and angular divergence approach 0.4 mm or less and at most 20 mrad, respectively. This unexpected, superior performance of the polycapillary optic in the extreme Ultraviolet could enable the design of an e cient, versatile and compact spectrometer for inverse photoemission spectroscopy (IPES): Its wavelength-dispersive component, a customized reflection zone plate, can maintain an energy resolution of 0.3 eV, whereas the sensitivity may be enhanced by more than one order of magnitude, compared to conventional spectrometers. Furthermore, the overall length of 0.9 m would allow for an eased alignment and evacuation. We see a significant potential for numerous polycapillary-based XUV / soft X-ray instruments in the future, in particular after further optimization for this long wavelength regime

Highly efficient soft x-ray spectrometer for transient absorption spectroscopy with broadband table-top high harmonic sources

We present a novel soft x-ray spectrometer for ultrafast absorption spectroscopy utilizing table-top femtosecond high-order harmonic sources. Where most commercially available spectrometers rely on spherical variable line space gratings with a typical efficiency on the order of 3% in the first diffractive order, this spectrometer, based on a Hettrick–Underwood design, includes a reflective zone plate as a dispersive element. An improved efficiency of 12% at the N K-edge is achieved, accompanied by a resolving power of 890. The high performance of the soft x-ray spectrometer is further demonstrated by comparing nitrogen K-edge absorption spectra from calcium nitrate in aqueous solution obtained with our high-order harmonic source to previous measurements performed at the electron storage ring facility BESSY II

Metropolis revisited: dialectic of enlightenment, modernity and architectural modernizm

Theodor Adorno ve Max Horkheimer, 'Aydınlanma'nın Diyalektiği: Felsefi Fragmanlar' (1947) adlı yapıtlarında, Aydınlanma projesinin yapısı gereği totaliter olduğunu ve mitolojiyi insan düşüncesinden kovmuş olmasına rağmen kendisinin mite gerilediğini öne sürmektedirler. Aydınlanma paradigmasının ürünü olan birer sanat dalı olarak erken 20. yüzyıl sineması ve mimarlık, Adorno ve Horkheimer'in bu savlarını doğrulamaktadırlar. Fritz Lang'in Metropolis (1927) adlı filmi; bir paradig- ma değişimi olarak Aydınlanma'nın, tarihsel bir dönem olarak Modernite'nin ve bu tarihsel döneme özgü bir üslup olarak Modern Mimari hareketin birbirleri ile ilişkilerinin çözümlenebilmesine olanak sağlayan çok katmanlı bir anlamsal yapı- ya sahiptir. Filmde Aydınlanma-mitoloji ile Modern Mimari-tarihsel içerik diyalektikleri paralel olarak işlenmiştir. Filmdeki, Metropolis'in makine estetiğine dayalı fütüristik ütopik mimarisi ile distopik tekno-totaliter toplumsal düzen arasındaki gerilim, gerçekte tarihsel üsluplardan yararlanmayı reddeden Modern Mimari hareketin ütopik karakteri ile mitoloji olarak tarihsel birikim arasındaki gerilimi yansıtmaktadır. Theodor Adorno and Max Horkheimer asserted that the project of enlightenment which itself is already totalitarian ai- med to overthrow the myths from the human mind and to install human beings as masters reverted to mythology at the end, in their master work 'Dialectic of Enlightment: Philosophical Fragments' (1947). As artistic products of Enlightment Project, cinema and architecture of early twentieth century affirmed Adorno and Horkheimer's thesis. Fritz Lang's Metro- polis (1927)'s multi-layered messages enables us to comprehend the relationships between Enlightment as a paratigmatic change, Modernity as a historical period, Architectural Modernism as an artistic style which is a product of this paradigm and this historical period. In this film, dialectics of Enlightment/mitology and Architectural Modernism/historical content entwined. In reality, the tension between utopian futuristic architecture based on machine aesthetics of Metropolis and its distopian techno-totaliterian social order reflected the tension between utopian characteristic of Modern Avant-garde in architecture who rejects to use historical styles and historical content as mitology

Combining scanning probe microscopy and x-ray spectroscopy

A new versatile tool, combining Shear Force Microscopy and X-Ray Spectroscopy was designed and constructed to obtain simultaneously surface topography and chemical mapping. Using a sharp optical fiber as microscope probe, it is possible to collect locally the visible luminescence of the sample. Results of tests on ZnO and on ZnWO4 thin layers are in perfect agreement with that obtained with other conventional techniques. Twin images obtained by simultaneous acquisition in near field of surface topography and of local visible light emitted by the sample under X-Ray irradiation in synchrotron environment are shown. Replacing the optical fibre by an X-ray capillary, it is possible to collect local X-ray fluorescence of the sample. Preliminary results on Co-Ti sample analysis are presented

a versatile optical pump–soft X-ray probe facility with 100 fs X-ray pulses of variable polarization

Here the major upgrades of the femtoslicing facility at BESSY II (Khan et al., 2006) are reviewed, giving a tutorial on how elliptical-polarized ultrashort soft X-ray pulses from electron storage rings are generated at high repetition rates. Employing a 6 kHz femtosecond-laser system consisting of two amplifiers that are seeded by one Ti:Sa oscillator, the total average flux of photons of 100 fs duration (FWHM) has been increased by a factor of 120 to up to 106 photons s-1 (0.1% bandwidth)-1 on the sample in the range from 250 to 1400 eV. Thanks to a new beamline design, a factor of 20 enhanced flux and improvements of the stability together with the top-up mode of the accelerator have been achieved. The previously unavoidable problem of increased picosecond- background at higher repetition rates, caused by `halo' photons, has also been solved by hopping between different `camshaft' bunches in a dedicated fill pattern (`3+1 camshaft fill') of the storage ring. In addition to an increased X-ray performance at variable (linear and elliptical) polarization, the sample excitation in pump-probe experiments has been considerably extended using an optical parametric amplifier that supports the range from the near-UV to the far-IR regime. Dedicated endstations covering ultrafast magnetism experiments based on time-resolved X-ray circular dichroism have been either upgraded or, in the case of time-resolved resonant soft X-ray diffraction and reflection, newly constructed and adapted to femtoslicing requirements. Experiments at low temperatures down to 6 K and magnetic fields up to 0.5 T are supported. The FemtoSpeX facility is now operated as a 24 h user facility enabling a new class of experiments in ultrafast magnetism and in the field of transient phenomena and phase transitions in solids

Broadband Time-Delay and Chirp Compensator for X-ray Pulses

A new type of aberration-corrected time-delay compensating monochromator (TDCM) for soft X-rays is presented. Composed of two identical reflection zone plates (RZPs) on spherical substrates and an intermediate flat mirror for band-pass selection, the TDCM can operate in a wide energy range of about ±20% around the design energy of 410eV. Assuming a source size of 50μm and an angular acceptance of 1 mrad, the spectral resolving power may reach 6×102, at a pulse length as short as 4.3femtoseconds(fs). In the case of μm-sized sources, the resolution can be better than 0.1eV and the sub-fs regime could become accessible. The overall transmission efficiency varies within (4.2–6.0)% across the energy range (310–510) eV. In the complementary mode, chirped-pulse compression works as well. Depending on the properties of the source, simulations predict an up to 9-fold reduction in pulse duration, whereas ≤50% of the peak intensity is maintained

Li K Emissions Detection In Various Compounds Using A Reflection Zone Plate Spectrometer

International audienceSoft x-ray emission spectroscopy (XES) is a technique used to study the electronic structure of materials. It measures the energy spectrum of emitted x-rays from a sample. It is performed by irradiating the sample with ionizing particles (electrons in our case) and measuring the energy distribution of the x-rays that are subsequently emitted. The emitted x-rays are characteristic of the electronic states of the sample, thus, the presence of an element can be detected and could be also used to perform quantitative analysis.Reflection zone plates (RZP) can be used in XES as a wavelength-dispersive element [1]. They consist of a series of concentric zones, each with a slightly different thickness. When x-rays are incident on the zone plate, the different zones act as diffraction gratings, causing the x-rays to diffract and interfere with one another while focusing them at the same time. They have higher spectral resolution and cover wider energy ranges compared to other optical elements such as periodic multilayers. RZPs allow the reach of energy resolutions as low as 0.49 eV at the Al L2,3 line (around 72 eV) [2]. With parallel detection of x-rays in contrast to conventional wavelength dispersive spectroscopy (WDS) spectrometers with a dispersive crystal (or multilayer) based on Rowland mounting they do not have a scanning mechanism. In this work, we demonstrate the use of a Fresnel (RZP) implemented in an electron microprobe for the detection of Li K (around 50-55 eV) emission in different lithium compounds. Li K emission is a characteristic emission band produced when Li 1s levels are ionized inside the material. However, it can be challenging to detect this emission due to its low fluorescence yield, re-absorption effects, and the presence of other spectral lines in the same energy range. We report on our measurements of the Li K emission bands in several lithium compounds with an RZP spectrometer. Our results demonstrate this approach’s potential for various applications in the field of x-ray spectroscopy.Acknowledgment: This research was funded by Agence Nationale de la Recherche in the framework of the SQLX Project (ANR-20-CE29-0022).References[1]A. Erko et al., Opt. Express, vol. 22, no. 14, p. 16897, Jul. 2014, doi: 10.1364/OE.22.016897.[2]A. Hafner et al., Opt. Express, vol. 23, no. 23, p. 29476, Nov. 2015, doi: 10.1364/OE.23.029476