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in creator/contributor: "MacDowell, Alastair A."

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Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler

A data acquisition technique and relevant program for suppression of one of the systematic effects, namely the ''ghost'' effect, of a second generation long trace profiler (LTP) is described. The ''ghost'' effect arises when there is an unavoidable cross-contamination of the LTP sample and reference signals into one another, leading to a systematic perturbation in the recorded interference patterns and, therefore, a systematic variation of the measured slope trace. Perturbations of about 1-2 {m… more

Date: April 28, 2005

Creator: Yashchuk, Valeriy V.; Irick, Steve C. & MacDowell, Alastair A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Air convection noise of pencil-beam interferometer for long traceprofiler

In this work, we investigate the effect of air convection onlaser-beam pointing noise essential for the long trace profiler (LTP). Wedescribe this pointing error with noise power density (NPD) frequencydistributions. It is shown that the NPD spectra due to air convectionhave a very characteristic form. In the range of frequencies from ~;0.05Hz to ~;0.5 Hz, the spectra can be modeled with an inverse-power-lawfunction. Depending on the intensity of air convection that is controlledwith a resistiv… more

Date: July 12, 2006

Creator: Yashchuk, Valeriy V.; Irick, Steve C.; MacDowell, Alastair A.; McKinney, Wayne R. & Takacs, Peter Z.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Characterizing the Nano and Micro Structure of Concrete toImprove its Durability

New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images of ice inside cement paste and cracking caused by the alkali?silica reaction (ASR) enables three-dimens… more

Date: January 13, 2009

Creator: Monteiro, Paulo J. M.; Kirchheim, A. P.; Chae, S.; Fischer, Peter; MacDowell, Alastair A.; Schaible, Eirc et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Two Dimensional Power Spectral Density Measurements of X-Rayoptics With the Micromap Interferometric Microscope

A procedure and software have been developed to transform the area distribution of the residual surface heights available from the measurement with the Micromap interferometric microscope into a two-dimensional (2D) power spectral density (PSD) distribution of the surface height. The procedure incorporates correction of one of the spectral distortions of the PSD measurement. The distortion appears as a shape difference between the tangential and sagittal PSD spectra deduced from the 2D PSD dist… more

Date: May 12, 2005

Creator: Yashchuk, Valeriy V.; Franck, Andrew D.; C., Irick Steve; Howells,Malcolm R.; MacDowell, Alastair A. & McKinney, Wayne R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Crosscheck of different techniques for two dimensional power spectral density measurements of x-ray optics

The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It was shown that these three techniq… more

Date: July 12, 2005

Creator: Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cross-check of different techniques for two-dimensional powerspectral density measurements of X-ray optics

Date: April 17, 2005

Creator: Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Bendable X-ray Optics at the ALS: Design, Tuning, Performance and Applications

We review the development at the Advanced Light Source (ALS) of bendable x-ray optics widely used for focusing of beams of soft and hard x-rays. Typically, the focusing is divided in the tangential and sagittal directions into two elliptically cylindrical reflecting elements, the so-called Kirkpatrick-Baez (KB) pair [1]. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. This is in contrast to flat opt… more

Date: September 8, 2008

Creator: Advanced Light Source, Lawrence Berkeley National Laboratory; Yashchuk, Valeriy V.; Church, Matthew N.; Knight, Jason W.; Kunz, Martin; MacDowell, Alastair A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface Roughness of Stainless Steel Bender Mirrors for Focusing Soft X-rays

We have used polished stainless steel as a mirror substrate to provide focusing of soft x-rays in grazing incidence reflection. The substrate is bent to an elliptical shape with large curvature and high stresses in the substrate require a strong elastic material. Conventional material choices of silicon or of glass will not withstand the stress required. The use of steel allows the substrates to be polished and installed flat, using screws in tapped holes. The ultra-high-vacuum bender mechanism… more

Date: October 11, 2005

Creator: Yashchuk, Valeriy V.; Gullikson, Eric M.; Howells, Malcolm R.; Irick, Steve C.; MacDowell, Alastair A.; McKinney, Wayne R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Flat-Field Calibration of CCD Detector for Long TraceProfilers

The next generation of synchrotrons and free electron lasersrequires x-ray optical systems with extremely high-performance,generally, of diffraction limited quality. Fabrication and use of suchoptics requires highly accurate metrology. In the present paper, wediscuss a way to improve the performance of the Long Trace Profiler(LTP), a slope measuring instrument widely used at synchrotron facilitiesto characterize x-ray optics at high-spatial-wavelengths fromapproximately 2 mm to 1 m. One of the … more

Date: July 31, 2007

Creator: Kirschman, Jonathan L.; Domning, Edward E.; Franck, Keith D.; Irick, Steve C.; MacDowell, Alastair A.; McKinney, Wayne R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

SIBYLS - A SAXS and protein crystallography beamline at the ALS

The new Structurally Integrated BiologY for Life Sciences (SIBYLS) beamline at the Advanced Light Source will be dedicated to Macromolecular Crystallography (PX) and Small Angle X-ray Scattering (SAXS). SAXS will provide structural information of macromolecules in solutions and will complement high resolution PX studies on the same systems but in a crystalline state. The x-ray source is one of the 5 Tesla superbend dipoles recently installed at the ALS that allows for a hard x-ray program to be… more

Date: August 22, 2003

Creator: Trame, Christine; MacDowell, Alastair A.; Celestre, Richard S.; Padmore, Howard A.; Cambie, Daniella; Domning, Edward E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Progress on PEEM3 - An Aberration Corrected X-Ray PhotoemissionElectron Microscope at the ALS

A new ultrahigh-resolution photoemission electron microscope called PEEM3 is being developed and built at the Advanced Light Source (ALS). An electron mirror combined with a much-simplified magnetic dipole separator is to be used to provide simultaneous correction of spherical and chromatic aberrations. It is installed on an elliptically polarized undulator (EPU) beamline, and will be operated with very high spatial resolution and high flux to study the composition, structure, electric and magn… more

Date: May 20, 2006

Creator: MacDowell, Alastair A.; Feng, J.; DeMello, A.; Doran, A.; Duarte,R.; Forest, E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Beamline for High-Pressure Studies at the Advanced Light Sourcewith a Superconducting Bending Magnet as the Source

A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on Beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 Tesla superconducting bending magnet (superbend). Useful x-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness preserving optics of the beamline. These optics are comprised of… more

Date: June 30, 2005

Creator: Kunz, Martin; MacDowell, Alastair A.; Caldwell, Wendel A.; Cambie, Daniella; Celestre, Richard S.; Domning, Edward E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A dedicated superbend x-ray microdiffraction beamline for materials, geo-, and environmental sciences at the advanced light source

A new facility for microdiffraction strain measurements and microfluorescence mapping has been built on beamline 12.3.2 at the advanced light source of the Lawrence Berkeley National Laboratory. This beamline benefits from the hard x-radiation generated by a 6 T superconducting bending magnet (superbend) This provides a hard x-ray spectrum from 5 to 22 keV and a flux within a 1 mu m spot of ~;;5x109 photons/ s (0.1percent bandwidth at 8 keV). The radiation is relayed from the superbend source t… more

Date: March 24, 2009

Creator: Lawrence Berkeley National Laboratory. Advanced Light Source.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Suite of three protein crystallography beamlines with single superconducting bend magnet as the source

At the Advanced Light Source (ALS), three protein crystallography (PX) beamlines have been built that use as a source one of the three 6 Tesla single pole superconducting bending magnets (superbends) that were recently installed in the ring. The use of such single pole superconducting bend magnets enables the development of a hard x-ray program on a relatively low energy 1.9 GeV ring without taking up insertion device straight sections. The source is of relatively low power, but due to the smal… more

Date: August 1, 2004

Creator: MacDowell, Alastair A.; Celestre, Richard S.; Howells, Malcolm; McKinney, Wayne; Krupnick, James; Cambie, Daniella et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department