The Use op Field Emission Tubes in X-Ray Analysis

1971 ◽  
Vol 15 ◽  
pp. 285-294 ◽  
Author(s):  
J. H. McCrary ◽  
Ted Van Vorous
Keyword(s):  
Steady State ◽  
Field Emission ◽  
High Voltage ◽  
Absorption Edge ◽  
Power Supply ◽  
Quantitative Measure ◽  
X Rays ◽  
Absorption Analysis ◽  
X Ray ◽  
X Ray Absorption

Recently developed, miniature, steady state, field emission tubes are finding application in several areas of x-ray analysis. These tubes require only a high voltage, low current power supply to produce relatively intense beams of x-rays. Since anodes can be fabricated from almost any element, and since the tubes can be operated at potentials up to about 70 kV, many different output x-ray spectra are available. Miniaturized battery operated x-ray sources of this type, occupying a volume of about one liter, have several advantages over radioisotope sources. These include cost, safety, and controllable output spectra and intensity. X-ray sources for energy dispersive fluorescence analyzers are designed so that no scattered characteristic radiations will interfer with the analysis of the sample fluorescence. Sources which are essentially monoenergetic can be fabricated for use in non-dispersive x-ray fluorescence analyzers. Because of the intensity and safety of the field emission tubes, such analyzers can be made which are sensitive while compact, portable, and inexpensive. In x-ray absorption analysis the measurement of absorption edge jump ratios provides a quantitative measure of sample impurities. Field emission tubes whose output spectra consist primarily of bremsstrahlung are particularly well suited to such measurements. The techniques involved in using these tubes in x-ray analysis are described.

X-Ray absorption edge elemental imaging of B. thuringienis

1989 ◽  
Vol 47 ◽  
pp. 212-213
Author(s):  
R. L. Stears
Keyword(s):  
Absorption Edge ◽  
Elemental Distribution ◽  
X Rays ◽  
Differential Absorption ◽  
Synchrotron Source ◽  
High Brightness ◽  
X Ray ◽  
Elemental Imaging ◽  
Cellular Integrity ◽  
X Ray Absorption

Because of the nature of the bacterial endospore, little work has been done on analyzing their elemental distribution and composition in the intact, living, hydrated state. The majority of the qualitative analysis entailed intensive disruption and processing of the endospores, which effects their cellular integrity and composition.Absorption edge imaging permits elemental analysis of hydrated, unstained specimens at high resolution. By taking advantage of differential absorption of x-ray photons in regions of varying elemental composition, and using a high brightness, tuneable synchrotron source to obtain monochromatic x-rays, contact x-ray micrographs can be made of unfixed, intact endospores that reveal sites of elemental localization. This study presents new data demonstrating the application of x-ray absorption edge imaging to produce elemental information about nitrogen (N) and calcium (Ca) localization using Bacillus thuringiensis as the test specimen.

Study of Extended X-Ray Absorption Fine Structure with the Use of Thick Targets

1967 ◽  
Vol 11 ◽  
pp. 339-344
Author(s):  
J. T. Hach ◽  
E. W. White
Keyword(s):  
Fine Structure ◽  
Absorption Edge ◽  
Thick Target ◽  
Published Data ◽  
X Rays ◽  
X Ray ◽  
Fine Structures ◽  
Primary Advantage ◽  
Takeoff Angle ◽  
X Ray Absorption

AbstractA novel method has been investigated for the study of extended X-ray absorption-edge fine structures. The method takes advantage of the absorption of continuum X-rays that emerge at low takeoff angles from an electron-bombarded target. The extended fine structure is observed as undulations in the continuum X-ray intensity in the region of the self-absorption edge. Spectra from conventional X-ray diffraction tubes have been recorded for various values of kilovolts and takeoff angles. Spectra obtained by this method are compared with published data. Nearly all the features of the extended fine structures can be clearly resolved by this technique. In the case of iron ar.d copper targets, it is found, experimentally that the best contrast is obtained when using a 50-kV accelerating voltage. A takeoff angle of 3° yielded best results for copper, while an angle of 10° was best suited for iron. The Philibert absorption correction successfully used in electron microprobe analysis has been extended to account for the observed self-absorption effect where κΔλ = f(x)λ1/f(x)λ2. The primary advantage of the thick-target technique is in the ability to obtain absorption spectra without having to prepare thin films. The technique is essentially nondestructive in that the sample need not be pulverized or thinned.

Comparison of high-angle take-off and low-angle take-off EDX detector geometry of the HF-2000 FE-TEM

1993 ◽  
Vol 51 ◽  
pp. 252-253
Author(s):  
Y. Sato ◽  
T. Hashimoto ◽  
M. Ichihashi ◽  
Y. Ueki ◽  
K. Hirose ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Field Emission ◽  
Solid Angle ◽  
Energy Dispersive ◽  
Objective Lens ◽  
X Rays ◽  
High Angle ◽  
X Ray ◽  
Detector Geometry

Analytical TEMs have two variations in x-ray detector geometry, high and low angle take off. The high take off angle is advantageous for accuracy of quantitative analysis, because the x rays are less absorbed when they go through the sample. The low take off angle geometry enables better sensitivity because of larger detector solid angle.Hitachi HF-2000 cold field emission TEM has two versions; high angle take off and low angle take off. The former allows an energy dispersive x-ray detector above the objective lens. The latter allows the detector beside the objective lens. The x-ray take off angle is 68° for the high take off angle with the specimen held at right angles to the beam, and 22° for the low angle take off. The solid angle is 0.037 sr for the high angle take off, and 0.12 sr for the low angle take off, using a 30 mm2 detector.

scholarly journals Al-driven peculiarities of local coordination and magnetic properties in single-phase Alx-CrFeCoNi high-entropy alloys

Nano Research ◽  
2021 ◽  
Author(s):  
Alevtina Smekhova ◽  
Alexei Kuzmin ◽  
Konrad Siemensmeyer ◽  
Chen Luo ◽  
Kai Chen ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Magnetic Circular Dichroism ◽  
Surface Region ◽  
Face Centered Cubic ◽  
X Rays ◽  
X Ray ◽  
High Entropy ◽  
X Ray Absorption ◽  
Absorption Edges

AbstractModern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic properties. Herein, peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic (fcc)- and body-centered cubic (bcc)-structured high-entropy Alx-CrFeCoNi alloys (x = 0.3 and 3, respectively) are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy ranges. Simulations based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high precision. The revealed unimodal and bimodal distributions of all five elements are in agreement with structure-dependent magnetic properties of studied alloys probed by magnetometry. A degree of surface atoms oxidation uncovered by soft X-rays suggests different kinetics of oxide formation for each type of constituents and has to be taken into account. X-ray magnetic circular dichroism technique employed at L2.3 absorption edges of transition metals demonstrates reduced magnetic moments of 3d metal constituents in the sub-surface region of in situ cleaned fcc-structured Al0.3-CrFeCoNi compared to their bulk values. Extended to nanostructured versions of multicomponent alloys, such studies would bring new insights related to effects of high entropy mixing on low dimensions.

scholarly journals Synchrotron X-ray induced acoustic imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seongwook Choi ◽  
Eun-Yeong Park ◽  
Sinyoung Park ◽  
Jong Hyun Kim ◽  
Chulhong Kim
Keyword(s):  
Acoustic Imaging ◽  
Signal Frequency ◽  
X Rays ◽  
Repetition Period ◽  
Linear Accelerators ◽  
X Ray ◽  
X Ray Computed ◽  
Medical Linear Accelerators ◽  
Ionizing Radiation Exposure ◽  
X Ray Absorption

AbstractX-ray induced acoustic imaging (XAI) is an emerging biomedical imaging technique that can visualize X-ray absorption contrast at ultrasound resolution with less ionizing radiation exposure than conventional X-ray computed tomography. So far, medical linear accelerators or industrial portable X-ray tubes have been explored as X-ray excitation sources for XAI. Here, we demonstrate the first feasible synchrotron XAI (sXAI). The synchrotron generates X-rays, with a dominant energy of 4 to 30 keV, a pulse-width of 30 ps, a pulse-repetition period of 2 ns, and a bunch-repetition period of 940 ns. The X-ray induced acoustic (XA) signals are processed in the Fourier domain by matching the signal frequency with the bunch-repetition frequency. We successfully obtained two-dimensional XA images of various lead targets. This novel sXAI tool could complement conventional synchrotron applications.

scholarly journals Semi-automated protein crystal mounting device for the sulfur single-wavelength anomalous diffraction method

2010 ◽  
Vol 43 (2) ◽  
pp. 341-346 ◽  
Author(s):  
Yu Kitago ◽  
Nobuhisa Watanabe ◽  
Isao Tanaka
Keyword(s):  
Diffraction Method ◽  
Systematic Errors ◽  
Protein Crystal ◽  
X Rays ◽  
Anomalous Diffraction ◽  
X Ray ◽  
Frozen Solution ◽  
Custom Made ◽  
Protein Molecules ◽  
X Ray Absorption

Use of longer-wavelength X-rays has advantages for the detection of small anomalous signals from light atoms, such as sulfur, in protein molecules. However, the accuracy of the measured diffraction data decreases at longer wavelengths because of the greater X-ray absorption. The capillary-top mounting method (formerly the loopless mounting method) makes it possible to eliminate frozen solution around the protein crystal and reduces systematic errors in the evaluation of small anomalous differences. However, use of this method requires custom-made tools and a large amount of skill. Here, the development of a device that can freeze the protein crystal semi-automatically using the capillary-top mounting method is described. This device can pick up the protein crystal from the crystallization drop using a micro-manipulator, and further procedures, such as withdrawal of the solution around the crystal by suction and subsequent flash freezing of the protein crystal, are carried out automatically. This device makes it easy for structural biologists to use the capillary-top mounting method for sulfur single-wavelength anomalous diffraction phasing using longer-wavelength X-rays.

Electronic structure ofMS(M=Ca,Mg,Fe,Mn): X-ray absorption analysis

2004 ◽  
Vol 69 (13) ◽  
Author(s):  
A. N. Kravtsova ◽  
I. E. Stekhin ◽  
A. V. Soldatov ◽  
X. Liu ◽  
M. E. Fleet
Keyword(s):  
Electronic Structure ◽  
Absorption Analysis ◽  
X Ray ◽  
X Ray Absorption

Evidence of x-ray absorption-edge shift as a function of luminescence wavelength in porous silicon

2000 ◽  
Vol 62 (15) ◽  
pp. 9911-9914 ◽  
Author(s):  
G. Dalba ◽  
N. Daldosso ◽  
P. Fornasini ◽  
M. Grimaldi ◽  
R. Grisenti ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Absorption Edge ◽  
X Ray ◽  
Absorption Edge Shift ◽  
X Ray Absorption

scholarly journals Anisotropy of X-ray Absorption Cross Section in CeCoGe3 Single Crystal

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 544
Author(s):  
Andrei Rogalev ◽  
Fabrice Wilhelm ◽  
Elena Ovchinnikova ◽  
Aydar Enikeev ◽  
Roman Bakonin ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Linear Dichroism ◽  
X Rays ◽  
Absorption Cross ◽  
X Ray ◽  
Measured Absorption ◽  
Linearly Polarized ◽  
X Ray Absorption ◽  
Absorption Edges

Absorption spectra of two orthogonal linearly polarized x-rays in a single CeCoGe3 crystal were measured at the ID12 beamline of the ESRF for the energies near the K-edges of Ge, Co and near the L23 edges of Ce. The X-ray natural linear dichroism (XNLD) was revealed in the vicinity of all the absorption edges, which indicates a splitting of electronic states in a crystalline field. Mathematical modelling in comparison with experimental data allowed the isotropic and anisotropic parts of atomic absorption cross section in CeCoGe3 to be determined near all measured absorption edges. The calculations also show that the “average” anisotropy of the cross section close to the Ge K-edge revealed in the experiment is less than the partial anisotropic contributions corresponding to Ge atoms in two different Wyckoff positions.

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