High energy X-rays - AbsoluteAstronomy.com

High energy X-rays or HEX-rays are very hard X-rays, with typical energies of 80 keV

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Kev can refer to:*Kev Hawkins, a fictional character.*Kevin, a given name occasionally shortened to "Kev".*Kiloelectronvolt, a unit of energy who symbol is "KeV".* Krefelder Eislauf-VereinKEV can refer to:...

- 1000 keV

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(1 MeV), about one order of magnitude higher than conventional X-rays (and well into gamma-ray energies over 120 keV). They are produced at modern synchrotron radiation

Synchrotron radiation

The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...

sources such as the beamline ID15 at the European Synchrotron Radiation Facility

European Synchrotron Radiation Facility

The European Synchrotron Radiation Facility is a joint research facility supported by 19 countries situated in Grenoble, France...

(ESRF). The main benefit is the deep penetration into matter

Matter

Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...

which makes them a probe for thick samples in physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

and materials science

Materials science

Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...

and permits an in-air sample environment and operation. Scattering angles are small and diffraction directed forward allows for simple detector setups.

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 (or 12 to 120 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 has a curvature ten times smaller than in the low energy case and allows whole regions to be mapped in a reciprocal lattice
Reciprocal lattice
In physics, the reciprocal lattice of a lattice is the lattice in which the Fourier transform of the spatial function of the original lattice is represented. This space is also known as momentum space or less commonly k-space, due to the relationship between the Pontryagin duals momentum and...

, 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
Brillouin zone
In mathematics and solid state physics, the first Brillouin zone is a uniquely defined primitive cell in reciprocal space. The boundaries of this cell are given by planes related to points on the reciprocal lattice. It is found by the same method as for the Wigner–Seitz cell in the Bravais 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 analysis.
Simple diffraction setups due to operation in air.
Diffraction in forward direction for easy registration with a 2D detector.
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.
Forward scattering and penetration make sample environments easy and straight forward.
Neutron-like, but complementary studies combined with high precision spatial resolution.
Cross sections for Compton scattering
Compton scattering
In physics, Compton scattering is a type of scattering that X-rays and gamma rays undergo in matter. The inelastic scattering of photons in matter results in a decrease in energy of an X-ray or gamma ray photon, called the Compton effect...

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
BlueScope Steel
BlueScope Steel is a flat product steel producer with operations in Australia, New Zealand, Asia, the Pacific and North America. It was spun off from BHP Billiton in 2002 as BHP Steel and renamed BlueScope Steel on 17 November 2003...

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.

External links

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Advantages

Applications

See also

External links