High energy X-rays
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High-energy X-rays or HEX-rays are very hard
X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10 nanometers, corresponding to frequencies in the range 30&nbs ...
, with typical energies of 80–1000 
keV Kev can refer to: Given name * Kev Adams, French comedian, actor, screenwriter and film producer born Kevin Smadja in 1991 * Kevin Kev Carmody (born 1946), Indigenous Australian singer-songwriter * Kev Coghlan (born 1988), Scottish Grand Prix moto ...
(1 MeV), about one order of magnitude higher than conventional X-rays used for
X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
(and well into
gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically sh ...
energies over 120 keV). They are produced at modern synchrotron radiation sources such as the beamline ID15 at the
European Synchrotron Radiation Facility The European Synchrotron Radiation Facility (ESRF) is a joint research facility situated in Grenoble, France, supported by 22 countries (13 member countries: France, Germany, Italy, the UK, Spain, Switzerland, Belgium, the Netherlands, Denmark, ...
(ESRF). The main benefit is the deep penetration into
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...
which makes them a probe for thick samples in
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
and materials science and permits an in-air sample environment and operation. Scattering angles are small and diffraction directed forward allows for simple detector setups. High energy (megavolt) X-rays are also used in
cancer therapy Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bl ...
, using beams generated by
linear accelerator A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear ...
s to suppress tumors.Graham A. Colditz, '' The SAGE Encyclopedia of Cancer and Society'', SAGE Publications, 2015, page 1329


Advantages

High-energy X-rays (HEX-rays) between 100 and 300 keV bear unique advantage over conventional hard X-rays, which lie in the range of 5–20 keV They can be listed as follows: *High penetration into materials due to a strongly reduced photo absorption cross section. The photo-absorption strongly depends on the atomic number of the material and the X-ray energy. Several centimeter thick volumes can be accessed in steel and millimeters in lead containing samples. *No radiation damage of the sample, which can pin incommensurations or destroy the chemical compound to be analyzed. *The
Ewald sphere The Ewald sphere is a geometric construction used in electron, neutron, and X-ray crystallography which demonstrates the relationship between: :* the wavevector of the incident and diffracted x-ray beams, :* the diffraction angle for a given ref ...
has a curvature ten times smaller than in the low energy case and allows whole regions to be mapped in a
reciprocal lattice In physics, the reciprocal lattice represents the Fourier transform of another lattice (group) (usually a Bravais lattice). In normal usage, the initial lattice (whose transform is represented by the reciprocal lattice) is a periodic spatial fu ...
, similar to electron diffraction. *Access to diffuse scattering. This is absorption and not extinction limited at low energies while volume enhancement takes place at high energies. Complete 3D maps over several
Brillouin zone In mathematics and solid state physics, the first Brillouin zone is a uniquely defined primitive cell in reciprocal space. In the same way the Bravais lattice is divided up into Wigner–Seitz cells in the real lattice, the reciprocal lattice ...
s can be easily obtained. *High momentum transfers are naturally accessible due to the high momentum of the incident wave. This is of particular importance for studies of liquid, amorphous and nanocrystalline materials as well as
pair distribution function The pair distribution function describes the distribution of distances between pairs of particles contained within a given volume. Mathematically, if ''a'' and ''b'' are two particles in a fluid, the pair distribution function of ''b'' with respect ...
analysis. *Realization of the Materials oscilloscope. *Simple diffraction setups due to operation in air. *Diffraction in forward direction for easy registration with a 2D detector. Forward scattering and penetration make sample environments easy and straight forward. *Negligible polarization effects due to relative small scattering angles. *Special non-resonant magnetic scattering. * LLL interferometry. *Access to high-energy spectroscopic levels, both electronic and nuclear. *Neutron-like, but complementary studies combined with high precision spatial resolution. *Cross sections for
Compton scattering Compton scattering, discovered by Arthur Holly Compton, is the scattering of a high frequency photon after an interaction with a charged particle, usually an electron. If it results in a decrease in energy (increase in wavelength) of the photon ...
are similar to coherent scattering or absorption cross sections.


Applications

With these advantages, HEX-rays can be applied for a wide range of investigations. An overview, which is far from complete: *Structural investigations of real materials, such as metals, ceramics, and liquids. In particular, in-situ studies of phase transitions at elevated temperatures up to the melt of any metal. Phase transitions, recovery, chemical segregation, recrystallization, twinning and domain formation are a few aspects to follow in a single experiment. *Materials in chemical or operation environments, such as electrodes in batteries, fuel cells, high-temperature reactors, electrolytes etc. The penetration and a well-collimated pencil beam allows focusing in the region and material of interest while it undergoes a chemical reaction. *Study of 'thick' layers, such as oxidation of steel in its production and rolling process, which are too thick for classical reflectometry experiments. Interfaces and layers in complicated environments, such as the intermetallic reaction of Zincalume surface coating on industrial steel in the liquid bath. *In situ studies of industrial like strip casting processes for light metals. A casting setup can be set up on a beamline and probed with the HEX-ray beam in real time. *Bulk studies in single crystals differ from studies in surface-near regions limited by the penetration of conventional X-rays. It has been found and confirmed in almost all studies, that critical scattering and correlation lengths are strongly affected by this effect. *Combination of neutron and HEX-ray investigations on the same sample, such as contrast variations due to the different scattering lengths. *Residual stress analysis in the bulk with unique spatial resolution in centimeter thick samples; in-situ under realistic load conditions. *In-situ studies of thermo-mechanical deformation processes such as forging, rolling, and extrusion of metals. *Real time texture measurements in the bulk during a deformation, phase transition or annealing, such as in metal processing. *Structures and textures of geological samples which may contain heavy elements and are thick. *High resolution triple crystal diffraction for the investigation of single crystals with all the advantages of high penetration and studies from the bulk. *Compton spectroscopy for the investigation of momentum distribution of the valence electron shells. *Imaging and tomography with high energies. Dedicated sources can be strong enough to obtain 3D tomograms in a few seconds. Combination of imaging and diffraction is possible due to simple geometries. For example, tomography combined with residual stress measurement or structural analysis.


See also

*
Bremsstrahlung ''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typicall ...
*
Cyclotron radiation Cyclotron radiation is electromagnetic radiation emitted by non-relativistic accelerating charged particles deflected by a magnetic field. The Lorentz force on the particles acts perpendicular to both the magnetic field lines and the particles' mot ...
*
Electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) li ...
*
Electron–positron annihilation Electron–positron annihilation occurs when an electron () and a positron (, the electron's antiparticle) collide. At low energies, the result of the collision is the annihilation of the electron and positron, and the creation of energetic photo ...
*
Gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
* Gamma-ray generation *
Ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecul ...
*
Synchrotron light source A synchrotron light source is a source of electromagnetic radiation (EM) usually produced by a storage ring, for scientific and technical purposes. First observed in synchrotrons, synchrotron light is now produced by storage rings and other ...
* Synchrotron radiation *
X-radiation An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30  ...
*
X-ray fluorescence X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis ...
*
X-ray generator An X-ray generator is a device that produces X-rays. Together with an X-ray detector, it is commonly used in a variety of applications including medicine, X-ray fluorescence, electronic assembly inspection, and measurement of material thicknes ...
*
X-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...


References


Further reading

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External links

* {{cite journal , doi=10.1016/j.actamat.2006.04.004 , title=Recrystallization and phase transitions in a γ-Ti ''Al''-based alloy as observed by ex situ and in situ high-energy X-ray diffraction , year=2006 , last1=Liss , first1=Klaus-Dieter , last2=Bartels , first2=Arno , last3=Clemens , first3=Helmut , last4=Bystrzanowski , first4=Slawomir , last5=Stark , first5=Andreas , last6=Buslaps , first6=Thomas , last7=Schimansky , first7=Frank-Peter , last8=Gerling , first8=Rainer , last9=Scheu , first9=Christina , last10=Schreyer , first10=Andreas , display-authors=1 , journal=Acta Materialia , volume=54 , issue=14 , pages=3721–3735 , bibcode=2006AcMat..54.3721L Applied and interdisciplinary physics Gamma rays Materials testing Synchrotron radiation Synchrotron-related techniques X-rays