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photons
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Image
Published: 01 January 1986
Fig. 1 Absorption of a photon. (a) Ground state. (b) Transition. (c) Excited state
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Image
Published: 01 August 2018
Fig. 17 Calculated mass absorption coefficient for uranium as a function of photon energy (solid line) and contributions of various atomic processes (dashed lines). Rayleigh scattering is the difference between total scattering and Compton scattering.
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Image
Published: 15 December 2019
Fig. 6 XPS emission process for a model atom. An incoming photon causes the ejection of a photoelectron (a). The relaxation process results in an emission process of an Auger electron (b) KL 23 L 23 . The final arrangement results in a two-electron vacancy at the L 2,3 or 2p level ( Ref 8 ).
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Image
Published: 15 December 2019
Fig. 9 XPS machine (Kratos AXIS Ultra) with a fracture stage, ultraviolet photon source, Auger attachment, and reaction cell (at the back, not shown). Courtesy of Marshall Space Flight Center
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Image
Published: 15 June 2020
Fig. 5 (a) Stimulated absorption of a photon. (b) Spontaneous emission or the nonradiative transition of energy in a two-level system. (c) Stimulated emission of a photon. Transitions are shown to occur between lower ( E 1 ) and upper ( E 2 ) energy levels, where each filled-in circle
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Image
Published: 15 June 2020
Fig. 14 Photonic Doppler velocimetry (PDV). (a) Experimental setup for the PDV technique used. (b) Relative velocity vs. time for an unsuccessful bond. (c) Relative velocity vs. time for a successful bond. Source: Ref 82
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Image
Published: 15 December 2019
Fig. 7 (a) MIKROGAP detector with sample output. (b) Hybrid photon detector with example output (reprinted from Ref 13 with permission of Wiley. Copyright © International Union of Crystallography). (c) Micro x-ray diffraction Rigaku image plate system with simulated diffraction reflections
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Image
Published: 15 December 2019
Fig. 26 Generation of Auger electron and x-ray photon by inner shell ionization of an atom and subsequent electron transitions
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Image
Published: 15 December 2019
Fig. 1 Schematic of energy-level diagrams showing (a) x-ray photon emission and (b) Auger electron emission. Courtesy of Physical Electronics, USA
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Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005630
EISBN: 978-1-62708-174-0
.... Courtesy of IPG Photonics An optical fiber propagates light down its length through the principle of total internal reflection. The numerical aperture (NA) is the solid angle over which the fiber optic can accept light. A fiber optic input NA will be the same as its output NA, provided...
Abstract
Properly designed beam-delivery optics is essential to quality of the beam acting on the workpiece and to the economics of the manufacturing process. This article describes the design considerations of laser beam delivery optics. It also reviews the manufacturing economics and presents two case studies of typical economic environments found in laser welding applications.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005641
EISBN: 978-1-62708-174-0
... than that observed in electron beam welding, because the kinetic energy of electrons with rest mass (inertia) is greater than that of the photons (with zero rest mass) in the laser beam. For example, the maximum thickness of type 304 stainless steel plate that can be welded using a 77 kW CO 2 laser...
Abstract
This article provides an overview of the fundamentals, mechanisms, process physics, advantages, and limitations of laser beam welding. It describes the independent and dependent process variables in view of their role in procedure development and process selection. The article includes information on independent process variables such as incident laser beam power and diameter, laser beam spatial distribution, traverse speed, shielding gas, depth of focus and focal position, weld design, and gap size. Dependent variables, including depth of penetration, microstructure and mechanical properties of laser-welded joints, and weld pool geometry, are discussed. The article also reviews the various injuries and electrical and chemical hazards associated with laser beam welding.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005631
EISBN: 978-1-62708-174-0
Abstract
This article describes the joint preparation, fit-up and design of various types of laser beam weld joints: butt joint, lap joint, flange joint, kissing weld, and wire joint. It explains the use of consumables for laser welding and highlights the special laser welding practices of steel, aluminum, and titanium engineering alloys. Laser weld quality and quality assessment are described with summaries of imperfections and how its operations contribute to providing repeatable and reliable laser welds. Relevant laser weld quality specifications are listed.
Image
Published: 01 December 1998
Fig. 5 Schematic of energy dispersive x-ray detector. Detector measures the energy of each incoming x-ray photon by counting the number of electron-hole pairs it produces. A histogram is then developed and plotted of the x-ray energies of the many (typically tens to hundreds of thousands
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Image
Published: 15 December 2019
Fig. 1 The energy gap (Δ E ) between the ground state ( g ) and excited state ( g *) of a species changes during a spot test reaction. The value of Δ E is equal to the energy of a photon ( E photon ) that the molecule can absorb, which depends on Planck’s constant ( h ), the speed of light
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Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003250
EISBN: 978-1-62708-199-3
... are excited to higher quantum states (energy levels) or removed from the atom (ionization). These “excited” atoms quickly “relax” by electrons from higher energy levels filling the vacated levels. When this happens, photons are emitted whose energies are equal to the differences between the two energy levels...
Abstract
The overall chemical composition of metals and alloys is most commonly determined by X-ray fluorescence (XRF) and optical emission spectroscopy (OES), and combustion and inert gas fusion analysis. This article provides information on the capabilities, uses, detection threshold and precision methods, and sample requirements. The amount of material that needs to be sampled, operating principles, and limitations of the stated methods are also discussed.
Series: ASM Handbook
Volume: 10
Publisher: ASM International
Published: 15 December 2019
DOI: 10.31399/asm.hb.v10.a0006645
EISBN: 978-1-62708-213-6
... can easily provide detection limits for lead in soil of less than 100 ppm, well below typical regulatory levels of 300 to 1500 ppm. Operating Principles X-rays, discovered by Roentgen in 1895, are high-energy photons that occur from nuclear decay or when electrons in a disturbed or excited atom...
Abstract
This article provides a detailed account of X-ray spectroscopy used for elemental identification and determination. It begins with an overview of the operating principles of X-ray fluorescence (XRF) spectrometer, as well as a comparison of the operating principles of wavelength-dispersive spectrometer (WDS) and energy-dispersive spectrometer (EDS). This is followed by a discussion on the mechanism and effects of X-ray radiation, X-ray emission, and X-ray absorption. The article then discusses components used, operation, and applications of WDS and EDS. Some of the factors and processes involved in sample preparation for XRF analysis are also included. The article further provides information on the practical procedure for and the applications of WDS and EDS qualitative and quantitative analyses.
Series: ASM Handbook
Volume: 17
Publisher: ASM International
Published: 01 August 2018
DOI: 10.31399/asm.hb.v17.a0006459
EISBN: 978-1-62708-190-0
... Abstract Digital radiography is a technique that uses digital detector arrays (linear or area) to capture an X-ray photonic signal and convert it to an electronic signal for display on a computer. This article begins with an overview of real-time radiography and provides a schematic...
Abstract
Digital radiography is a technique that uses digital detector arrays (linear or area) to capture an X-ray photonic signal and convert it to an electronic signal for display on a computer. This article begins with an overview of real-time radiography and provides a schematic illustration of a typical radioscopic system using an X-ray image intensifier. It discusses the advantages and limitations of real-time radiography. Computed radiography (CR) is one of the radiography techniques that utilizes a reusable detector comprised of photostimuable luminescence (PSL) storage phosphor. The article provides a schematic illustration of a typical storage phosphor imaging plate. It concludes with a discussion on the benefits of digital radiography.
Series: ASM Handbook
Volume: 17
Publisher: ASM International
Published: 01 August 2018
DOI: 10.31399/asm.hb.v17.a0006448
EISBN: 978-1-62708-190-0
... light, and infrared radiation showing their relationship with wavelength and photon energy X-rays and γ-rays are physically indistinguishable; they differ only in the manner in which they are produced. X-rays result from the interaction between a rapidly moving stream of electrons and atoms...
Abstract
Radiography is the process or technique of producing images of a solid material on a paper/photographic film or on a fluorescent screen by means of radiation particles or electromagnetic waves of short wavelength. This article reviews the general characteristics and safety principles associated with radiography. There are two main aspects of safety: monitoring radiation dosage and protecting personnel. The article summarizes the major factors involved in both and discusses the operating characteristics of X-ray tubes. It describes the various methods of controlling scattered radiation: use of lead screens; protection against backscatter and scatter from external objects; and use of masks, diaphragms, collimators, and filtration. The article concludes with a discussion on image conversion media, including recording media, lead screens, lead oxide screens, and fluorescent intensifying screens.
Image
Published: 31 October 2011
Fig. 3 Output profiles for (a) single-mode fiber optic and (b) stepped-index fiber optic. Courtesy of IPG Photonics and Primes
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