An x-ray microprobe based upon a close-coupled focal-spot / glass capillary arrangement

1992 ◽  
Vol 50 (2) ◽  
pp. 1758-1759
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor
Keyword(s):  
Imaging Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Close Coupling ◽  
X Ray ◽  
Point To Point ◽  
Beam Damage

The development of intense sources of x rays has led to renewed interest in the use of microbeams of x rays in x-ray fluorescence analysis. Sparks pointed out that the use of x rays as a probe offered the advantages of high sensitivity, low detection limits, low beam damage, and large penetration depths with minimal specimen preparation or perturbation. In addition, the option of air operation provided special advantages for examination of hydrated systems or for nondestructive microanalysis of large specimens.The disadvantages of synchrotron sources prompted the development of laboratory-based instrumentation with various schemes to maximize the beam flux while maintaining small point-to-point resolution. Nichols and Ryon developed a microprobe using a rotating anode source and a modified microdiffractometer. Cross and Wherry showed that by close-coupling the x-ray source, specimen, and detector, good intensities could be obtained for beam sizes between 30 and 100μm. More importantly, both groups combined specimen scanning with modern imaging techniques for rapid element mapping.

Applications of a Laboratory X-ray Micropsobe to Materials Analysis

1988 ◽  
Vol 32 ◽  
pp. 115-120 ◽  
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor ◽  
C. E. Holcombe
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Materials Analysis ◽  
X Ray ◽  
Small Glass

A laboratory-based X-ray microprobe, composed of a high-brilliance microfocus X-ray tube, coupled with a small glass capillary, has been developed for materials applications. Because of total external reflectance of X rays from the smooth inside bore of the glass capillary, the microprobe has a high sensitivity as well as a high spatial resolution. The use of X rays to excite elemental fluorescence offers the advantages of good peak-to-background, the ability to operate in air, and minimal specimen preparation. In addition, the development of laboratory-based instrumentation has been of Interest recently because of greater accessibility when compared with synchrotron X-ray microprobes.

Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1038-1039
Author(s):  
Shawn Williams ◽  
Xiaodong Zhang ◽  
Susan Lamm ◽  
Jack Van’t Hof
Keyword(s):  
Visible Light ◽  
Radiation Damage ◽  
Cross Section ◽  
Imaging Techniques ◽  
Dose Range ◽  
Specimen Preparation ◽  
X Rays ◽  
Metaphase Chromosomes ◽  
X Ray ◽  
Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

Protein Crystallography Using Capillary-Focused X-Rays

1996 ◽  
Vol 54 ◽  
pp. 238-239
Author(s):  
D. X. Balaic ◽  
Z. Barnea ◽  
K. A. Nugent ◽  
R. F. Garrett ◽  
J. N. Varghese ◽  
...  
Keyword(s):  
Fluorescence Analysis ◽  
Focal Region ◽  
X Rays ◽  
Glass Capillary ◽  
Synchrotron Source ◽  
X Ray ◽  
Exit Aperture ◽  
Egg White Lysozyme ◽  
Diffraction Patterns ◽  
Focused Beam

Tapered glass capillaries for X-ray beam concentration have been a topic of much interest for the synchrotron X-ray community in recent years. These optics have long held the promise of high-intensity microbeam generation for the “hard” X-ray energies used in crystallography and fluorescence analysis.X-ray concentration is achieved by exploiting the total external reflection property of glass surfaces for glancing angles of incidence. X-rays directed into the entrance aperture of the capillary are reflected toward an exit aperture of smaller dimensions, resulting in an increased X-ray flux per unit area at the exit aperture. Capillary designs with a true geometrical focus beyond the capillary exit are also possible.Our group has recently demonstrated a paraboloidally-tapered glass capillary optic which produced a focused X-ray beam using a monochromatised synchrotron source. The optic was designed to produce a focal region for singly-reflected X-rays at a point 40 mm from the end of the capillary. Such a focal region was observed, with a FWHM intensity gain of two orders of magnitude over the incident X-ray intensity from the channel-cut monochromator. Moreover, this gain was achieved for X-ray energies from 5 to 20 keV. We subsequently used a similar optic to obtain X-ray diffraction patterns from a crystal of hen egg-white lysozyme on image plates. The use of the capillary-focused beam yielded diffraction patterns 70 to 100 times faster than using an unfocused beam from the channel-cut monochromator alone. Placement of the crystal at different positions in the capillary-focused beam demonstrated the focusing of Bragg reflections and diffraction from a small volume of crystal.

Micro-Analysis by X-Ray Absorption, Fluorescence, Emission and Diffraction Using Ultra-Fine X-Ray Sources

1957 ◽  
Vol 1 ◽  
pp. 329-337 ◽  
Author(s):  
V. E. Cosslett ◽  
P. Duncumb ◽  
J. V. P. Long ◽  
W. G. Nixon
Keyword(s):  
Line Emission ◽  
Fluorescence Emission ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Characteristic Line ◽  
X Rays ◽  
Emission Analysis ◽  
Thin Sections ◽  
X Ray ◽  
Micro Analysis

AbstractFine focus X-ray tubes developed for projection X-ray microscopy can also be used for X-ray micro-analysis. Areas about 10 microns in diameter of thin sections have been analyzed by measuring differences in X-ray transmission, with particular reference to the determination of calcium in biological materials and in minerals. The high intensity of this X-ray point source has permitted micro-fluorescence analysis of similar small areas with high sensitivity and reasonable time. The same electron optical system has been used for micro-emission analysis of rock slices and mineral grains. By scanning the electron beam over the specimen surface and recording either the scattered electrons or the emitted X-rays, a two-dimensional picture can be displayed of the physical features or of the distribution of a particular element respectively. The analysis of a selected, volume of 1 cubic micron in the surface has been obtained by plotting the characteristic line emission spectrum with a crystal spectrometer and proportional counter. The sensitivity is 0. 1% or 10−1 gram. Micro-beam X-ray diffraction has also been used with a stationary X-ray source both for transmission and back reflection with a 10 minute exposure from a 10 micron diameter area.

A Combined Photoelectron/X-Ray Fluorescence Spectrometer

1973 ◽  
Vol 17 ◽  
pp. 509-520
Author(s):  
H. K. Herglotz ◽  
D. R. Lynch
Keyword(s):  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Excitation Power ◽  
X Rays ◽  
X Ray ◽  
Analysis Instrument ◽  
Mode Of Operation ◽  
Excitation Mechanisms ◽  
Fluorescence Spectrometer ◽  
Advanced Version

AbstractFacilities for energy-dispersive x-ray fluorescence analysis have been added to an advanced version of the high-sensitivity ESCA (electron spectroscopy for chemical analysis) instrument described at the 1972 Denver Conference. Since the excitation mechanisms for electron emission and x-ray fluorescence are the same, the instrument's powerful source of primary x-rays is an asset to both types of spectroscopy. The geometrical arrangement of source, electron analyzer, and x-ray detector permits easy change from one mode of operation to the other without change of sample. While ESCA is valuable for the analysis of light elements and of surfaces apart from the bulk, x-ray fluorescence is useful for the analysis of bulk or substrate. The high excitation power makes the instrument useful also for trace analysis in solid or liquid samples. Modifications that could further enhance the usefulness of the instrument are described.

X-ray Fluorescence Analysis of Gold Ore

1996 ◽  
Vol 50 (5) ◽  
pp. 572-575 ◽  
Author(s):  
Benito De Celis
Keyword(s):  
Analytical Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
X Rays ◽  
Nondestructive Analysis ◽  
X Ray ◽  
Gold Ore ◽  
Large Samples ◽  
Radioisotope Source ◽  
The Matrix

A method to obtain high sensitivity and accuracy for nondestructive analysis of gold ore is proposed. The applied technique is energy-dispersive X-ray fluorescence, using a Co-57 radioisotope source to excite gold K X-rays in the sample, and a high-purity Ge (HPGe) detector with a range of energies from 1 keV to 4 MeV. The use of radioisotope sources and K X-rays gives some advantages in comparison with other analytical techniques and the usual tube excitation L X-ray analysis: the high sensitivity to concentrations of 1 ppm, the absence of interferences from other elements present in the matrix, and the possibility of performing fast and economical nondestructive analyses of large samples.

Applications of laboratory-based X-ray microbeam diffraction and fluorescence analysis

1994 ◽  
Vol 52 ◽  
pp. 58-59
Author(s):  
Brian R. York
Keyword(s):  
High Efficiency ◽  
Analytical Techniques ◽  
Fluorescence Analysis ◽  
Specimen Preparation ◽  
X Rays ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wave Guides ◽  
Diffraction Patterns

The quantitative structural and chemical analysis of bulk materials is generally done using x-ray diffraction and fluorescence techniques. This is due, in large part, to the vast body of work which has gone into characterizing the x-ray scattering process and the ease with which this interaction canbe kinematically modeled to high precision. Other salient features of x-ray analytical techniques aretheir use as subsurface probes, they require minimal specimen preparation, and ambient conditions are generally adequate for analysis. However, as microanalytical tools, these techniques were typically abandoned because of the difficulty encountered in confining the x-rays to dimensions <<.1 mm with sufficient intensity for a timely analysis. Recently, there has been a rekindled interestin x-ray microbeam analysis because of the reintroduction of tapered capillaries as total reflection x-ray optics. Tapered capillaries can essentially capture larger solid angles nearer the x-ray sourceand act as x-ray wave guides to transport the x-rays to the specimen with high efficiency. It is now possible using laboratory x-ray sources, to produce x-ray beams suitable for diffraction or fluorescence analysis, with diameters in the range of 3-12 μm. X-ray diffraction patterns have been acquired from diffraction volumes as small as 2 μm and fluorescence maps with 5 μm spatialresolution have been demonstrated.

X-ray Gabor holography

1995 ◽  
Vol 53 ◽  
pp. 612-613
Author(s):  
Steve Lindaas ◽  
Chris Jacobsen ◽  
Alex Kalinovsky ◽  
Malcolm Howells
Keyword(s):  
Surface Relief ◽  
Biological Imaging ◽  
Specimen Preparation ◽  
X Rays ◽  
X Ray ◽  
Water Window ◽  
Biological Objects ◽  
Transmission Imaging ◽  
Atomic Force ◽  
Electron Microscopes

Soft x-ray microscopy offers an approach to transmission imaging of wet, micron-thick biological objects at a resolution superior to that of optical microscopes and with less specimen preparation/manipulation than electron microscopes. Gabor holography has unique characteristics which make it particularly well suited for certain investigations: it requires no prefocussing, it is compatible with flash x-ray sources, and it is able to use the whole footprint of multimode sources. Our method serves to refine this technique in anticipation of the development of suitable flash sources (such as x-ray lasers) and to develop cryo capabilities with which to reduce specimen damage. Our primary emphasis has been on biological imaging so we use x-rays in the water window (between the Oxygen-K and Carbon-K absorption edges) with which we record holograms in vacuum or in air.The hologram is recorded on a high resolution recording medium; our work employs the photoresist poly(methylmethacrylate) (PMMA). Following resist “development” (solvent etching), a surface relief pattern is produced which an atomic force microscope is aptly suited to image.

XRMF applications of a monolithic, polycapillary, focusing x-ray optic

1996 ◽  
Vol 54 ◽  
pp. 240-241
Author(s):  
D. A. Carpenter ◽  
Ning Gao ◽  
G. J. Havrilla
Keyword(s):  
Trace Elements ◽  
Point Source ◽  
Focal Spot ◽  
Fluorescence Analysis ◽  
X Rays ◽  
Focal Distance ◽  
Spot Diameter ◽  
X Ray ◽  
Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

scholarly journals Optimization of X-ray Investigations in Dentistry Using Optical Coherence Tomography

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4554
Author(s):  
Ralph-Alexandru Erdelyi ◽  
Virgil-Florin Duma ◽  
Cosmin Sinescu ◽  
George Mihai Dobre ◽  
Adrian Bradu ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Radiation Dose ◽  
Imaging Techniques ◽  
Image Resolution ◽  
Optical Coherence ◽  
X Rays ◽  
High Quality ◽  
X Ray

The most common imaging technique for dental diagnoses and treatment monitoring is X-ray imaging, which evolved from the first intraoral radiographs to high-quality three-dimensional (3D) Cone Beam Computed Tomography (CBCT). Other imaging techniques have shown potential, such as Optical Coherence Tomography (OCT). We have recently reported on the boundaries of these two types of techniques, regarding. the dental fields where each one is more appropriate or where they should be both used. The aim of the present study is to explore the unique capabilities of the OCT technique to optimize X-ray units imaging (i.e., in terms of image resolution, radiation dose, or contrast). Two types of commercially available and widely used X-ray units are considered. To adjust their parameters, a protocol is developed to employ OCT images of dental conditions that are documented on high (i.e., less than 10 μm) resolution OCT images (both B-scans/cross sections and 3D reconstructions) but are hardly identified on the 200 to 75 μm resolution panoramic or CBCT radiographs. The optimized calibration of the X-ray unit includes choosing appropriate values for the anode voltage and current intensity of the X-ray tube, as well as the patient’s positioning, in order to reach the highest possible X-rays resolution at a radiation dose that is safe for the patient. The optimization protocol is developed in vitro on OCT images of extracted teeth and is further applied in vivo for each type of dental investigation. Optimized radiographic results are compared with un-optimized previously performed radiographs. Also, we show that OCT can permit a rigorous comparison between two (types of) X-ray units. In conclusion, high-quality dental images are possible using low radiation doses if an optimized protocol, developed using OCT, is applied for each type of dental investigation. Also, there are situations when the X-ray technology has drawbacks for dental diagnosis or treatment assessment. In such situations, OCT proves capable to provide qualitative images.

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