Rigorous calculations and synchrotron radiation measurements of diffraction efficiencies for tender X-ray lamellar gratings: conical versus classical diffraction

2018 ◽  
Vol 25 (6) ◽  
pp. 1683-1693 ◽  
Author(s):  
Leonid Goray ◽  
Werner Jark ◽  
Diane Eichert
Keyword(s):  
Spectral Range ◽  
High Efficiency ◽  
Promising Result ◽  
Surface Profile ◽  
Incident Beam ◽  
Integral Equation Method ◽  
Grazing Incidence ◽  
Boundary Integral ◽  
Lower Efficiency ◽  
X Ray

When reflection gratings are operated at grazing incidence in the extreme off-plane configuration and the incident beam trajectory is parallel to the grooves, the diffraction into the first order can be more efficient than in the classical orientation. This situation is referred to as the conical diffraction case. In the classical configuration the grooves are perpendicular to the incident beam and thus an efficiency-reducing shadowing effect will be observed at very grazing angles. It was recently shown that a laminar grating could provide symmetric and relatively high efficiencies in conical diffraction for diffraction even of photons with large energies of the order of 4 and 6 keV. For photon energies in the tender X-ray range, accurate computing tools for the calculation of diffraction efficiencies from gratings with simple coatings have not been available. Promising results for this spectral range now require the development of tools for modelling the diffraction efficiency expected in optical instrumentation, in which the provision of high efficiency in the indicated spectral range is mandatory. This is the case when weak sources are to be investigated, like in space science. In this study it will be shown that scalar calculations are not appropriate for this purpose, while newly introduced rigorous calculations based on the boundary integral equation method, implemented in the PCGrate ® code, can provide predictions that are in agreement with observed diffraction efficiencies. The agreement is achieved by modelling the exact surface profile. This applies for both the conical diffraction configuration and for the classical in-plane configuration, in which a significantly lower efficiency was obtained. Even though the profile of the presented grating was not perfect, but significantly distorted, the calculations show that efficiency-wise the structure provided already more than 75% of the ideally expected efficiency for conical diffraction. This is a very promising result for further optimization of diffraction gratings for use in the tender X-ray range.

A high-efficiency and high-spectral-resolution EUV/soft X-ray monochromator based on off-plane diffraction

2020 ◽  
Vol 27 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Werner Jark
Keyword(s):  
Spectral Resolution ◽  
High Efficiency ◽  
Extreme Ultraviolet ◽  
Incident Beam ◽  
Grazing Incidence ◽  
Incident Radiation ◽  
High Spectral Resolution ◽  
X Ray ◽  
Grating Monochromator ◽  
Plane Diffraction

The most efficient diffraction at a periodic grating structure is expected to take place when the incident radiation can be considered to have been specularly reflected off the inclined part of grooves that are positioned parallel to the trajectory of the incident beam. Very encouraging results for this configuration, in which the diffraction takes place off-plane, have been reported recently for a grating to be used in a spectrometer for space science investigations. This grating provided high efficiency for a relatively large groove density and a large blaze angle. High efficiency was observed even in higher diffraction orders up to the fourth order. Here the performance parameters, especially for the combination of diffraction efficiency and achievable spectral resolution, will be discussed for a grating used in a grazing-incidence plane-grating monochromator for monochromatization of synchrotron radiation in the extreme ultraviolet (EUV) and soft X-ray range with photon energies between 30 eV and 2000 eV. It is found that the instrument can provide competitive spectral resolution in comparison with the use of in-plane diffraction. In the case of comparable spectral resolution, the off-plane diffraction is found to provide superior efficiency.

scholarly journals Closely packed, low reorganization energy π-extended postfullerene acceptors for efficient polymer solar cells

2018 ◽  
Vol 115 (36) ◽  
pp. E8341-E8348 ◽  
Author(s):  
Steven M. Swick ◽  
Weigang Zhu ◽  
Micaela Matta ◽  
Thomas J. Aldrich ◽  
Alexandra Harbuzaru ◽  
...  
Keyword(s):  
Solar Cells ◽  
Density Functional ◽  
High Efficiency ◽  
Performance Metrics ◽  
Polymer Solar Cells ◽  
Reorganization Energy ◽  
Grazing Incidence ◽  
Scanning Calorimetry ◽  
Quantum Chemical Analysis ◽  
X Ray

New organic semiconductors are essential for developing inexpensive, high-efficiency, solution-processable polymer solar cells (PSCs). PSC photoactive layers are typically fabricated by film-casting a donor polymer and a fullerene acceptor blend, with ensuing solvent evaporation and phase separation creating discrete conduits for photogenerated holes and electrons. Until recently, n-type fullerene acceptors dominated the PSC literature; however, indacenodithienothiophene (IDTT)-based acceptors have recently enabled remarkable PSC performance metrics, for reasons that are not entirely obvious. We report two isomeric IDTT-based acceptors 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz-(5, 6)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]di-thiophene (ITN-C9) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz(6,7)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITzN-C9) that shed light on the exceptional IDTT properties vis-à-vis fullerenes. The neat acceptors and blends with fluoropolymer donor poly{[4,8-bis[5-(2- ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF) are investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, single-crystal X-ray diffraction, photovoltaic response, space-charge-limited current transport, atomic force microscopy, grazing incidence wide-angle X-ray scattering, and density functional theory-level quantum chemical analysis. The data reveal that ITN-C9 and ITzN-C9 organize such that the lowest unoccupied molecular orbital-rich end groups have intermolecular π−π distances as close as 3.31(1) Å, with electronic coupling integrals as large as 38 meV, and internal reorganization energies as small as 0.133 eV, comparable to or superior to those in fullerenes. ITN-C9 and ITzN-C9 have broad solar-relevant optical absorption, and, when blended with PBDB-TF, afford devices with power conversion efficiencies near 10%. Performance differences between ITN-C9 and ITzN-C9 are understandable in terms of molecular and electronic structure distinctions via the influences on molecular packing and orientation with respect to the electrode.

scholarly journals Refitting an X-ray diffraction system for combined GIXRF and XRR measurements

2020 ◽  
Vol 35 (S1) ◽  
pp. S29-S33
Author(s):  
Dieter Ingerle ◽  
Werner Artner ◽  
Klaudia Hradil ◽  
Christina Streli
Keyword(s):  
Incident Beam ◽  
Fluorescence Analysis ◽  
Grazing Incidence ◽  
Performance Criteria ◽  
Nickel Layer ◽  
Beam Optics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Special Software ◽  
Spectrometer Data

A commercial Empyrean X-ray diffractometer was adapted for combined grazing incidence X-ray fluorescence analysis (GIXRF) measurements with X-ray reflectivity (XRR) measurements. An energy-dispersive silicon drift detector was mounted and integrated in the angle-dependent data acquisition of the Empyrean. Different monochromator/X-ray optics units have been compared with the values obtained by the Atominstitut GIXRF + XRR spectrometer. Data evaluation was performed by JGIXA, a special software for combined GIXRF + XRR data fitting, developed at Atominstitut. A sample consisting of a ~50 nm nickel layer on a silicon substrate was used to compare the performance criteria (i.e. divergence and intensity) of the incident beam optics. An Empyrean X-ray diffractometer was successfully refitted to measure both GIXRF and XRR data.

The theory, manufacture, structure and performance of n.p.l. x-ray gratings

1975 ◽  
Vol 277 (1271) ◽  
pp. 503-543 ◽  
Keyword(s):  
Diffraction Efficiency ◽  
Incidence Angle ◽  
Surface Profile ◽  
Wavelength Region ◽  
Grazing Incidence ◽  
Diffraction Theory ◽  
Groove Depth ◽  
X Ray ◽  
Scalar Diffraction ◽  
And Performance

X-ray gratings have been developed for use in the wavelength region of 0.01-20 nm, where it is required to employ a grazing incidence configuration. The gratings have a rectangular profile and radiation is diffracted both from the tops and bottoms of the grooves. They therefore differ from blazed gratings, used at grazing incidence, in that a substantial portion of the grating participates in the diffraction process. A scalar diffraction theory has been developed which demonstrates that grating diffraction efficiency varies periodically with wavelength, pitch, groove depth and incidence angle. The theory can be used to optimize grating parameters for most efficient use in any selected region of the spectrum. The gratings are produced by processing a ruled 300 lines per millimetre master grating, so that surface profile defects introduced by ruling are eliminated. Grating performance has been assessed by means of a specially designed grating analyser in addition to spectrometers and a spectrograph. The experimental results are in qualitative agreement with theory. At very short wavelengths of 0.05 nm and grazing incidence angles of about 5', the diffraction efficiency in the first order is below 1 %. The efficiency rises rapidly to between 5 and 10 % at 0.15 nm and to 20 % in the 1 nm region where the incidence angles are typically a few degrees.

Generalized grazing-incidence-angle X-ray diffraction (G-GIXD) using image plates

1998 ◽  
Vol 5 (3) ◽  
pp. 488-490 ◽  
Author(s):  
Yasuo Takagi ◽  
Masao Kimura
Keyword(s):  
Incidence Angle ◽  
Incident Beam ◽  
Grazing Incidence ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface And Interface ◽  
Out Of Plane ◽  
Grazing Incidence Angle ◽  
Interface Layers

A new and more `generalized' grazing-incidence-angle X-ray diffraction (G-GIXD) method which enables simultaneous measurements both of in- and out-of-plane diffraction images from surface and interface structures has been developed. While the method uses grazing-incidence-angle X-rays like synchrotron radiation as an incident beam in the same manner as in `traditional' GIXD, two-dimensional (area) detectors like image plates and a spherical-type goniometer are used as the data-collection system. In this way, diffraction images both in the Seemann–Bohlin (out-of-plane) and GIXD geometry (in-plane) can be measured simultaneously without scanning the detectors. The method can be applied not only to the analysis of the in-plane crystal structure of epitaxically grown thin films, but also to more general research topics like the structural analysis of polycrystalline mixed phases of thin surface and interface layers.

Application of a single-reflection collimating multilayer optic for X-ray diffraction experiments employing parallel-beam geometry

2008 ◽  
Vol 41 (1) ◽  
pp. 124-133 ◽  
Author(s):  
M. Wohlschlögel ◽  
T. U. Schülli ◽  
B. Lantz ◽  
U. Welzel
Keyword(s):  
Incident Beam ◽  
Grazing Incidence ◽  
Photon Flux ◽  
Data Sets ◽  
Parallel Beam ◽  
X Ray ◽  
Beam Focusing ◽  
Beam Geometry ◽  
Parallel Beam Geometry ◽  
Diffraction Patterns

Instrumental aberrations of a parallel-beam diffractometer equipped with a rotating anode X-ray source, a single-reflection collimating multilayer optic and a parallel-plate collimator in front of the detector have been investigated on the basis of standard measurements (i.e.employing stress- and texture-free isotropic powder specimens exhibiting small or negligible structural diffraction line broadening). It has been shown that a defocusing correction, which is a major instrumental aberration for diffraction patterns collected with divergent-beam (focusing) geometries, is unnecessary for this diffractometer. The performance of the diffractometer equipped with the single-reflection collimating multilayer optic (single-reflection mirror) is compared with the performance of the diffractometer equipped with a Kirkpatrick–Baez optic (cross-coupled Göbel mirror) on the basis of experimental standard measurements and ray-tracing calculations. The results indicate that the use of the single-reflection mirror provides a significant gain in photon flux and brilliance. A high photon flux, high brilliance and minimal divergence of the incident beam make the setup based on the single-reflection mirror particularly suitable for grazing-incidence diffraction, and thus for the investigation of very thin films (yielding low diffracted intensities) and of stress and texture (requiring the acquisition of large measured data sets, corresponding to the variation of the orientation of the diffraction vector with respect to the specimen frame of reference). A comparative discussion of primary optics which can be used to realise parallel-beam geometry shows the range of possible applications of parallel-beam diffractometers and indicates the virtues and disadvantages of the different optics.

LOCAL STRUCTURE OF PHOTO-INDUCED PHASES PROBED BY X-RAY ABSORPTION SPECTROSCOPY: PHOTO-INDUCED ANISOTROPY IN CHALCOGENIDE GLASSES

2002 ◽  
Vol 16 (11n12) ◽  
pp. 1721-1730 ◽  
Author(s):  
H. OYANAGI ◽  
A. KOLOBOV ◽  
K. TANAKA
Keyword(s):  
Absorption Spectroscopy ◽  
Local Structure ◽  
Chalcogenide Glasses ◽  
High Efficiency ◽  
Grazing Incidence ◽  
Amorphous Selenium ◽  
Fluorescence Excitation ◽  
Excitation Light ◽  
X Ray ◽  
X Ray Absorption

We describe X-ray absorption spectroscopy (XAS) technique to probe the local structure of photo-induced phase. Photo-induced melting of chalcogenide glass (amorphous selenium, a-Se) was investigated. A grazing-incidence fluorescence excitation and a high efficiency X-ray detector were used to detect a small change of coordination number due to photo-induced transformation. It was shown that photo-induced three-fold coordinated sites are formed upon light irradiation forming cross-linking between selenium chains (photo-induced melting). A simple model is proposed which describes the reorientation of selenium chain perpendicular to the polarization direction of excitation light leading to photo-induced dichroism (anisotropy). Potential of XAS as a local probe of nanoscale structural modifications induced by photo-excitation is clearly demonstrated.

Theoretical considerations in the construction of hard X-ray resonators at inclined incidence with ultra-high efficiency and resolution

2016 ◽  
Vol 49 (5) ◽  
pp. 1653-1658 ◽  
Author(s):  
Y.-H. Wu ◽  
Y.-Y. Chang ◽  
Y.-W. Tsai ◽  
S.-L. Chang
Keyword(s):  
High Efficiency ◽  
Incident Beam ◽  
Normal Incidence ◽  
Dynamical Theory ◽  
X Ray ◽  
Multiple Beam ◽  
Back Reflection ◽  
Diffraction Geometry ◽  
Fabry Perot ◽  
Beam Diffraction

Detailed considerations of how to construct inclined-incidence hard X-ray resonators are presented. Owing to the symmetry of the crystals used, the Bragg back reflection usually employed in normal-incidence two- and multi-plate resonators to reflect the X-ray beam is often accompanied by unavoidable multiple-beam diffraction, and thus the reflectivity and cavity finesse are quite low. In contrast, crystal-based Fabry–Perot (FP) resonators at inclined incidence utilize multiple-beam diffraction to excite the back reflection inside the resonator to generate FP resonance with high efficiency, while avoiding the incident beam suffering from crystal absorption. The useful characteristics of inclined-incidence resonators are derived from numerical calculations based on the inclined-incidence diffraction geometry and the dynamical theory. Experimental results with Laue inclined incidence are in accordance with the simulation. The sub-millielectronvolt energy resolution and ultra-high efficiency of the transmission spectrum of the proposed resonators are also described.

DEVELOPMENT OF A TARGET POSITIONING SYSTEM BASED ON A LASER POSITION SENSOR FOR HIGH-EFFICIENCY WAVELENGTH-DISPERSIVE PIXE ANALYSIS

2010 ◽  
Vol 20 (01n02) ◽  
pp. 1-9 ◽  
Author(s):  
S. WONGLEE ◽  
T. TADA ◽  
H. FUKUDA ◽  
J. HASEGAWA ◽  
Y. OGURI
Keyword(s):  
Proton Beam ◽  
High Efficiency ◽  
Surface Profile ◽  
Target Position ◽  
Target Surface ◽  
Beam Width ◽  
Positioning System ◽  
Position Sensor ◽  
Pixe Analysis ◽  
X Ray

A precise target positioning system based on a laser position sensor was developed for a high-efficiency wavelength dispersive PIXE analysis. The absolute position and the target surface profile were clearly observed using this position sensor, which was rigidly connected to the target vacuum chamber. By using a thin proton beam ( width = 2 mm ) and a small target (width = 1 mm), the optimum target position for the measurement of chlorine ( Cl ) Kβ X-ray could be determined from X-ray detection yields measured at various target positions. We found that the relationship between the X-ray detection yield and the target position can be explained by the target size as well as the incident proton beam width. After precise adjustment of the target position using the above system, target samples with two different Cl compounds, NaCl and NH 4 Cl , were successfully distinguished from the difference in the measured profiles of Kβ X-ray spectra.

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