Beam Size (beam + size)

Distribution by Scientific Domains

Selected Abstracts

Polycapillary-optics-based micro-XANES and micro-EXAFS at a third-generation bending-magnet beamline

Geert Silversmit
A focusing system based on a polycapillary half-lens optic has been successfully tested for transmission and fluorescence -X-ray absorption spectroscopy at a third-generation bending-magnet beamline equipped with a non-fixed-exit Si(111) monochromator. The vertical positional variations of the X-ray beam owing to the use of a non-fixed-exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K -edge is approximately 200,m on the lens input side and this was reduced to ,1,m for the focused beam. Beam sizes (FWHM) of 12,16,m, transmission efficiencies of 25,45% and intensity gain factors, compared with the non-focused beam, of about 2000 were obtained in the 7,14,keV energy range for an incoming beam of 0.5 2,mm (vertical horizontal). As a practical application, an As K -edge -XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant. [source]

Q-Switched Ruby Laser Treatment for Postsclerotherapy Hyperpigmentation

Alireza Tafazzoli
Background. One of the most common adverse sequelae of sclerotherapy is cutaneous hyperpigmentation. Objective. We used the Q-switched ruby laser to treat postsclerotherapy hyperpigmentation. Methods. Eight patients developed pigmentation lasting more than 1 year (1,2 years on average) after sclerotherapy treatment for reticular and telangiectatic veins in the legs ranging in size from 0.2 to 4 mm in diameter. All patients were treated with a Q-switched ruby laser at 694 nm, 4 mm beam size, and fluence range of 5.6,10.5 J/cm2. Results. Ninety-two percent of lesions lightened after treatment. There was significant (75,100%) resolution of hyperpigmentation in 58% of treated areas, 25% improvement in 33% of treated areas, and no improvement in the remaining areas. Conclusion. Our impression is that given a choice of lasers, the Q-switched ruby laser provides the greatest efficacy for treating postsclerotherapy hyperpigmentation. [source]

Ferromagnetic Spots in Graphite Produced by Proton Irradiation,

K.-h. Han
A proton microbeam produces ferromagnetic spots on a highly oriented graphite surface. The Figure shows the topography and the magnetic force microscopy (MFM) images obtained after irradiating the surface with a beam size of 1,,m,,1 ,m and a dose of 0.098 nC,,m,2. The strength of the magnetic signal is only a factor of ,,10 smaller than that obtained on Fe particles. [source]

Focusing capillary optics for use in solution small-angle X-ray scattering

Jessica S. Lamb
Measurements of the global conformation of macromolecules can be carried out using small-angle X-ray scattering (SAXS). Glass focusing capillaries, manufactured at the Cornell High Energy Synchrotron Source (CHESS), have been successfully employed for SAXS measurements on the heme protein cytochrome c. These capillaries provide high X-ray flux into a spot size of tens of micrometres, permitting short exposures of small-volume samples. Such a capability is ideal for use in conjunction with microfluidic mixers, where time resolution may be determined by beam size and sample volumes are kept small to facilitate mixing and conserve material. [source]

Microbeam small-angle scattering experiments and their combination with microdiffraction

C. Riekel
The brilliance of undulator X-ray sources can be used to develop microfocusing optics for wide-angle (WAXS) and small-angle (SAXS) X-ray scattering. At the ESRF microfocus beamline, a beam size of 10 ,m is obtained by a pinhole collimating system coupled to a double focusing mirror. This allows resolving the first order of collagen (67 nm). Glass capillary optics provides a beam size close to one micron, however, with a more limited resolution. A high-resolution CCD detector allows combined SAXS/WAXS experiments for one detector setting. [source]

Tephrological implications of beam size,sample-size effects in electron microprobe analysis of glass shards

John B. Hunt
Abstract This paper concerns the potential consequences of varying procedures for the determination of tephra geochemistry by electron microprobe. Application of electron probe microanalysis to tephrostratigraphical methods has increasingly facilitated the resolution and refinement of Quaternary chronology associated with records of proxy-environmental or proxy-climatic change. The geographical range over which tephras are recovered has expanded significantly with the identification and analysis of crypto (or hidden) tephras in areas far removed from tephra sources. These tephras are dominated by glass shards, which, in many distal environments, may be either small in size (,m) or may be highly pumiceous with low glass:void ratios and thin (<10 ,m) shard walls. We demonstrate that reducing the size of the electron beam used to analyse shard geochemistry cannot be used reliably to permit analysis of thin glass walls. This approach distorts the geochemical data, creating analytical differences that may generate inappropriate tephrogeochemical fingerprints. Additional distortion of the geochemical fingerprint in the form of hybrid analyses may be encountered in glass fragments containing micron-sized crystalline phases such as feldspar. Copyright 2001 John Wiley & Sons, Ltd. [source]

A dedicated small-angle X-ray scattering beamline with a superconducting wiggler source at the NSRRC

Din-Goa Liu
At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5,GeV storage ring, a dedicated small-angle X-ray scattering (SAXS) beamline has been installed with an in-achromat superconducting wiggler insertion device of peak magnetic field 3.1,T. The vertical beam divergence from the X-ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (,E/E, 2 10,4) in the energy range 5,23,keV, or by a double Mo/B4C multilayer monochromator for 10,30 times higher flux (,1011,photons,s,1) in the 6,15,keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ,0.9,mm 0.3 mm (horizontal vertical) at the focus point located 26.5,m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing-incidence SAXS (GISAXS) from liquid surfaces. Two online beam-position monitors separated by 8,m provide an efficient feedback control for an overall beam-position stability in the 10,m range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray-tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core-shell quantum dots) and GISAXS from liquid surfaces. [source]

Spatial resolution limits for synchrotron-based spectromicroscopy in the mid- and near-infrared

Erika Levenson
Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continum XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet. [source]

A sagittally focusing double-multilayer monochromator for ultrafast X-ray imaging applications

Jinyuan Liu
The development of a sagittally focusing double-multilayer monochromator is reported, which produces a spatially extended wide-bandpass X-ray beam from an intense synchrotron bending-magnet source at the Advanced Photon Source, for ultrafast X-ray radiography and tomography applications. This monochromator consists of two W/B4C multilayers with a 25, period coated on Si single-crystal substrates. The second multilayer is mounted on a sagittally focusing bender, which can dynamically change the bending radius of the multilayer in order to condense and focus the beam to various points along the beamline. With this new apparatus, it becomes possible to adjust the X-ray beam size to best match the area detector size and the object size to facilitate more efficient data collection using ultrafast X-ray radiography and tomography. [source]

Small-gap insertion-device development at the National Synchrotron Light Source , performance of the new X13 mini-gap undulator

J. M. Ablett
The National Synchrotron Light Source (NSLS) 2.8,GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman,Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical , function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25,cm-period mini-gap undulator, operating down to a gap of 3.3,mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range ,3.7,16,keV at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability. [source]

Recent developments in microdiffraction on protein crystals

Christian Riekel
Protein crystallography microdiffraction and micro small-angle X-ray scattering at a third-generation synchrotron radiation source undulator beamline both require a compromise on beam size and beam divergence. Micro small-angle X-ray scattering requires in addition an as-close-as-possible angular approach to the direct beam, which is mainly limited by the beam divergence at the sample position. Both techniques have been developed at the ESRF microfocus beamline in a complimentary way. The development of a dedicated microgoniometer in the frame of an EMBL/ESRF collaboration has revealed the potential of microdiffraction for protein crystallography and is a step in the quest for user friendly instrumentation. [source]

High-speed crystal detection and characterization using a fast-readout detector

Jun Aishima
A novel raster-scanning method combining continuous sample translation with the fast readout of a Pilatus P6M detector has been developed on microfocus beamline I24 at Diamond Light Source. This fast grid-scan tool allows the rapid evaluation of large sample volumes without the need to increase the beam size at the sample through changes in beamline hardware. A slow version is available for slow-readout detectors. Examples of grid-scan use in centring optically invisible samples and in detecting and characterizing numerous microcrystals on a mesh-like holder illustrate the most common applications of the grid scan now in routine use on I24. [source]

Two-dimensional visible synchrotron light interferometry for transverse beam-profile measurement at the SPring-8 storage ring

Mitsuhiro Masaki
A two-dimensional visible synchrotron light interferometer has been developed to measure the transverse profile of an electron beam at the SPring-8 storage ring. The new interferometer enables the simultaneous measurement of beam sizes along the major and minor axes and the beam-tilt angle of an assumed elliptical Gaussian distribution. The principle of the interferometer is explained through basic formulae. To calibrate the point-spread function of the interferometer, a simple error model was assumed for disturbances in the amplitude and phase of the light; these disturbances were presumably caused by optical elements, such as mirrors and lenses. The experimental method to determine the parameters in the error model is shown. To verify the two-dimensional profiling capabilities of the interferometer, an electron beam stored in the SPring-8 storage ring operated at various working points was observed. A beam broadening from 20 to 120,m in the vertical direction and changes in the beam-tilt angle were clearly observed at working points close to the differential resonance. However, the vertical spatial resolution is limited by the available vertical separation of the apertures of the diffracting mask because of the narrow aperture of the upstream vacuum duct. [source]