Coherent scattering of X-rays and high-speed electron rays by atoms The atomic form-factor

The scattering formula of Rutherford gives an expression for the number n 1 d Ω of electrons in a gas which are scattered from a beam of electrons over the solid angle d Ω by impacts with atoms, which are to be found along a certain length l of this beam. If + Z e is the charge of the nucleus of the atoms, — e and m the charge and the mass of the electron, V the potential difference through which the electrons are accelerated, N the number of atoms in unit volume and n 0 the total number of electrons which pass a certain cross-section of the beam, we have the well-known formula: n 1 d Ω = n 0 N l (Z e /4V) 2 d Ω/sin 4 ½Θ, (1) where Θ is the angle of scattering. When n 0 = 1, N = 1, and l = 1 the scattering is usually expressed by I θ d Ω, where I θ is the so-called “scattered intensity.’’ According to Rutherford’s formula we get for the classical scattering due to the nucleus: I θ = ( e /4V) 2 Z 2 /sin 4 ½Θ. (2) Taking into consideration the electrons around the nucleus Mott and Bethe find: I θ = ( e /4V) 2 (Z -F) 2 /sin 4 ½Θ, (3) where F is the atomic form factor, known from the scattering of X-rays, and also a function of (V sin 2 ½Θ). The values calculated for helium by James have been used for F in this paper.

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The effect of temperature on high-resolution TEM image contrast

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139573 ◽

1995 ◽

Vol 53 ◽

pp. 640-641

Author(s):

T. Geipel ◽

W. Mader ◽

P. Pirouz

Keyword(s):

Form Factor ◽

Inelastic Scattering ◽

Accurate Method ◽

Waller Factor ◽

Effect Of Temperature ◽

Specimen Thickness ◽

Influence Of Temperature ◽

Debye Waller Factor ◽

Influence Of Temperature On ◽

Atomic Form Factor

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).

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PHAX-SCAN: Functional integration of a Scanning Electron Microscope and an energy-dispersive x-ray analyser

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152252 ◽

1989 ◽

Vol 47 ◽

pp. 56-57

Author(s):

Marc H. Peeters ◽

Max T. Otten

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

High Speed ◽

High Performance ◽

Functional Integration ◽

Energy Dispersive ◽

X Rays ◽

X Ray ◽

High Speed Analysis ◽

Scanning Electron

Over the past decades, the combination of energy-dispersive analysis of X-rays and scanning electron microscopy has proved to be a powerful tool for fast and reliable elemental characterization of a large variety of specimens. The technique has evolved rapidly from a purely qualitative characterization method to a reliable quantitative way of analysis. In the last 5 years, an increasing need for automation is observed, whereby energy-dispersive analysers control the beam and stage movement of the scanning electron microscope in order to collect digital X-ray images and perform unattended point analysis over multiple locations.The Philips High-speed Analysis of X-rays system (PHAX-Scan) makes use of the high performance dual-processor structure of the EDAX PV9900 analyser and the databus structure of the Philips series 500 scanning electron microscope to provide a highly automated, user-friendly and extremely fast microanalysis system. The software that runs on the hardware described above was specifically designed to provide the ultimate attainable speed on the system.

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Influence of tool edge form factor and cutting parameters on milling performance

Advances in Mechanical Engineering ◽

10.1177/16878140211009041 ◽

2021 ◽

Vol 13 (4) ◽

pp. 168781402110090

Author(s):

Xuefeng Zhao ◽

Hao Qin ◽

Zhiguo Feng

Keyword(s):

Form Factor ◽

Simulation Model ◽

Cutting Force ◽

Surface Quality ◽

High Speed ◽

Orthogonal Cutting ◽

Cutting Temperature ◽

Tool Edge ◽

Drag Finishing ◽

Edge Preparation

Tool edge preparation can improve the tool life, as well as cutting performance and machined surface quality, meeting the requirements of high-speed and high-efficiency cutting. In general, prepared tool edges could be divided into symmetric or asymmetric edges. In the present study, the cemented carbide tools were initially edge prepared through drag finishing. The simulation model of the carbide cemented tool milling steel was established through Deform software. Effects of edge form factor, spindle speed, feed per tooth, axial, and radial cutting depth on the cutting force, the tool wear, the cutting temperature, and the surface quality were investigated through the orthogonal cutting simulation. The simulated cutting force results were compared to the results obtained from the orthogonal milling experiment through the dynamometer Kistler, which verified the simulation model correctness. The obtained results provided a basis for edge preparation effect along with high-speed and high effective cutting machining comprehension.

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From Femtoseconds to Hours–Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

Applied Sciences ◽

10.3390/app11136179 ◽

2021 ◽

Vol 11 (13) ◽

pp. 6179

Author(s):

Felix Lehmkühler ◽

Wojciech Roseker ◽

Gerhard Grübel

Keyword(s):

Time Scales ◽

Free Electron Laser ◽

Photon Correlation Spectroscopy ◽

Signal To Noise Ratio ◽

Coherent Scattering ◽

Correlation Spectroscopy ◽

X Rays ◽

Photon Correlation ◽

X Ray ◽

Scattering Technique

X-ray photon correlation spectroscopy (XPCS) enables the study of sample dynamics between micrometer and atomic length scales. As a coherent scattering technique, it benefits from the increased brilliance of the next-generation synchrotron radiation and Free-Electron Laser (FEL) sources. In this article, we will introduce the XPCS concepts and review the latest developments of XPCS with special attention on the extension of accessible time scales to sub-μs and the application of XPCS at FELs. Furthermore, we will discuss future opportunities of XPCS and the related technique X-ray speckle visibility spectroscopy (XSVS) at new X-ray sources. Due to its particular signal-to-noise ratio, the time scales accessible by XPCS scale with the square of the coherent flux, allowing to dramatically extend its applications. This will soon enable studies over more than 18 orders of magnitude in time by XPCS and XSVS.

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The SEXTANTS beamline at SOLEIL: a new facility for elastic, inelastic and coherent scattering of soft X-rays

Journal of Physics Conference Series ◽

10.1088/1742-6596/425/7/072018 ◽

2013 ◽

Vol 425 (7) ◽

pp. 072018 ◽

Cited By ~ 35

Author(s):

M Sacchi ◽

N Jaouen ◽

H Popescu ◽

R Gaudemer ◽

J M Tonnerre ◽

...

Keyword(s):

Coherent Scattering ◽

X Rays ◽

New Facility

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Detector commissioning and development for PETRA-III

Diamond Light Source Proceedings ◽

10.1017/s2044820110000043 ◽

2010 ◽

Vol 1 (SRMS-7) ◽

Cited By ~ 1

Author(s):

David Pennicard ◽

Heinz Graafsma ◽

Michael Lohmann

Keyword(s):

High Speed ◽

Materials Science ◽

Dynamic Range ◽

Photon Counting ◽

High Energy ◽

X Rays ◽

Silicon Detectors ◽

Time Resolved ◽

Wide Range ◽

Synchrotron Light

The new synchrotron light source PETRA-III produced its first beam last year. The extremely high brilliance of PETRA-III and the large energy range of many of its beamlines make it useful for a wide range of experiments, particularly in materials science. The detectors at PETRA-III will need to meet several requirements, such as operation across a wide dynamic range, high-speed readout and good quantum efficiency even at high photon energies. PETRA-III beamlines with lower photon energies will typically be equipped with photon-counting silicon detectors for two-dimensional detection and silicon drift detectors for spectroscopy and higher-energy beamlines will use scintillators coupled to cameras or photomultiplier tubes. Longer-term developments include ‘high-Z’ semiconductors for detecting high-energy X-rays, photon-counting readout chips with smaller pixels and higher frame rates and pixellated avalanche photodiodes for time-resolved experiments.

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