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X-ray optics is the branch of
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
that manipulates
X-ray 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&nb ...
s instead of
visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
. It deals with focusing and other ways of manipulating the X-ray beams for research techniques such as
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 ...
,
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 ...
,
small-angle X-ray scattering Small-angle X-ray scattering (SAXS) is a small-angle scattering technique by which nanoscale density differences in a sample can be quantified. This means that it can determine nanoparticle size distributions, resolve the size and shape of (monodi ...
,
X-ray microscopy An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations. Unlike visible li ...
, X-ray phase-contrast imaging, and X-ray astronomy. Since X-rays and visible light are both
electromagnetic waves 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) ...
they propagate in space in the same way, but because of the much higher
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
and
photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they alwa ...
energy of X-rays they interact with matter very differently. Visible light is easily redirected using lenses and
mirror A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the im ...
s, but because the real part of the
complex refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...
of all materials is very close to 1 for X-rays, they instead tend to initially penetrate and eventually get absorbed in most materials without changing direction much.


X-ray techniques

There are many different techniques used to redirect X-rays, most of them changing the directions by only minute angles. The most common principle used is
reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...
at grazing incidence angles, either using
total external reflection Total external reflection is a phenomenon traditionally involving X-rays, but in principle any type of electromagnetic or other wave, closely related to total internal reflection. Total internal reflection describes the fact that radiation (e.g. ...
at very small angles or multilayer coatings. Other principles used include
diffraction Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...
and interference in the form of
zone plate A zone plate is a device used to Focus (optics), focus light or other things exhibiting wave character.G. W. Webb, I. V. Minin and O. V. Minin, “Variable Reference Phase in Diffractive Antennas”, ''IEEE Antennas and Propagation Magazine'', ...
s,
refraction In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomen ...
in compound refractive lenses that use many small X-ray lenses in series to compensate by their number for the minute index of refraction, Bragg reflection from a crystal plane in flat or bent
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s. X-ray beams are often
collimated A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A perfectly collimated light beam, with no divergence, would not disperse with distance. However, diffraction p ...
or reduced in size using pinholes or movable slits typically made of tungsten or some other high- Z material. Narrow parts of an X-ray spectrum can be selected with
monochromator A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is from the Greek roots ''mono-'', ...
s based on one or multiple Bragg reflections by crystals. X-ray spectra can also be manipulated by having the X-rays pass through a
filter (optics) An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optica ...
. This will typically reduce the low-energy part of the spectrum, and possibly parts above absorption edges of the elements used for the filter.


Focusing optics

Analytical X-ray techniques such as X-ray crystallography, small-angle X-ray scattering,
wide-angle X-ray scattering In X-ray crystallography, wide-angle X-ray scattering (WAXS) or wide-angle X-ray diffraction (WAXD) is the analysis of Bragg peaks scattered to wide angles, which (by Bragg's law) are caused by sub-nanometer-sized structures. It is an X-ray-diffr ...
, X-ray fluorescence,
X-ray spectroscopy X-ray spectroscopy is a general term for several spectroscopic techniques for characterization of materials by using x-ray radiation. Characteristic X-ray spectroscopy When an electron from the inner shell of an atom is excited by the energy o ...
and
X-ray photoelectron spectroscopy X-ray photoelectron spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique based on the photoelectric effect that can identify the elements that exist within a material (elemental composition) or are covering its surface, ...
all benefit from high X-ray flux densities on the samples being investigated. This is achieved by focusing the divergent beam from the X-ray source onto the sample using one out of a range of focusing optical components. This is also useful for scanning probe techniques such as scanning transmission X-ray microscopy and scanning X-ray fluorescence imaging.


Polycapillary optics

Polycapillary lenses are arrays of small hollow glass tubes that guide the X-rays with many
total external reflection Total external reflection is a phenomenon traditionally involving X-rays, but in principle any type of electromagnetic or other wave, closely related to total internal reflection. Total internal reflection describes the fact that radiation (e.g. ...
s on the inside of the tubes. The array is tapered so that one end of the capillaries points at the X-ray source and the other at the sample. Polycapillary optics are achromatic and thus suitable for scanning fluorescence imaging and other applications where a broad X-ray spectrum is useful. They collect X-rays efficiently for photon energies of 0.1 to 30  keV and can achieve gains of 100 to 10000 in flux over using a
pinhole A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of en ...
at 100 mm from the X-ray source. Since only X-rays entering the capillaries within a very narrow angle will be totally internally reflected, only X-rays coming from a small spot will be transmitted through the optic. Polycapillary optics cannot image more than one point to another, so they are used for illumination and collection of X-rays.


Zone plates

Zone plates consist of a substrate with concentric zones of a phase-shifting or absorbing material with zones getting narrower the larger their radius. The zone widths are designed so that a transmitted wave gets
constructive interference In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...
in a single point giving a focus. Zone plates can be used as condensers to collect light, but also for direct full-field imaging in e.g. an X-ray microscope. Zone plates are highly
chromatic Diatonic and chromatic are terms in music theory that are most often used to characterize scales, and are also applied to musical instruments, intervals, chords, notes, musical styles, and kinds of harmony. They are very often used as a p ...
and usually designed only for a narrow energy span, making it necessary to have
monochromatic A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochro ...
X-rays for efficient collection and high-resolution imaging.


Compound refractive lenses

Since refractive indices at X-ray wavelengths are so close to 1, the
focal length The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foc ...
s of normal lenses get impractically long. To overcome this, lenses with very small radii of curvature are used, and they are stacked in long rows, so that the combined focusing power gets appreciable. Since the refractive index is less than 1 for X-rays, these lenses must be
concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon, a polygon which is not convex * Concave set In geometry, a subset o ...
to achieve focusing, contrary to visible-light lenses, which are
convex Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytop ...
for a focusing effect. Radii of curvature are typically less than a millimeter, making the usable X-ray beam width at most about 1 mm. To reduce the
absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...
of X-rays in these stacks, materials with very low atomic number such as
beryllium Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to for ...
or
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...
are typically used. Since the refractive index depends strongly on X-ray wavelength, these lenses are highly
chromatic Diatonic and chromatic are terms in music theory that are most often used to characterize scales, and are also applied to musical instruments, intervals, chords, notes, musical styles, and kinds of harmony. They are very often used as a p ...
, and the variation of the focal length with wavelength must be taken into account for any application.


Reflection

The basic idea is to reflect a beam of
X-ray 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&nb ...
s from a surface and to measure the intensity of X-rays reflected in the specular direction (reflected angle equal to incident angle). It has been shown that a reflection off a parabolic mirror followed by a reflection off a hyperbolic mirror leads to the focusing of X-rays. Since the incoming X-rays must strike the tilted surface of the mirror, the collecting area is small. It can, however, be increased by nesting arrangements of mirrors inside each other. The ratio of reflected intensity to incident intensity is the X-ray reflectivity for the surface. If the interface is not perfectly sharp and smooth, the reflected intensity will deviate from that predicted by the Fresnel reflectivity law. The deviations can then be analyzed to obtain the density profile of the interface normal to the surface. For films with multiple layers, X-ray reflectivity may show oscillations with wavelength, analogous to the Fabry–Pérot effect. These oscillations can be used to infer layer thicknesses and other properties.


Diffraction

In X-ray diffraction a beam strikes a crystal and diffracts into many specific directions. The angles and intensities of the diffracted beams indicate a three-dimensional density of
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...
s within the crystal. X-rays produce a diffraction pattern because their
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
typically has the same
order of magnitude An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic di ...
(0.1–10.0 nm) as the spacing between the atomic planes in the crystal. Each atom re-radiates a small portion of an incoming beam's intensity as a spherical wave. If the atoms are arranged symmetrically (as is found in a crystal) with a separation ''d'', these spherical waves will be
in phase In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it ...
(add constructively) only in directions where their path-length difference 2''d'' sin ''θ'' is equal to an integer multiple of the wavelength ''λ''. The incoming beam therefore appears to have been deflected by an angle 2''θ'', producing a ''reflection'' spot in the
diffraction pattern Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a ...
. X-ray diffraction is a form of
elastic scattering Elastic scattering is a form of particle scattering in scattering theory, nuclear physics and particle physics. In this process, the kinetic energy of a particle is conserved in the center-of-mass frame, but its direction of propagation is modif ...
in the forward direction; the outgoing X-rays have the same energy, and thus the same wavelength, as the incoming X-rays, only with altered direction. By contrast,
inelastic scattering In chemistry, nuclear physics, and particle physics, inelastic scattering is a fundamental scattering process in which the kinetic energy of an incident particle is not conserved (in contrast to elastic scattering). In an inelastic scattering proces ...
occurs when energy is transferred from the incoming X-ray to an inner-shell electron, exciting it to a higher
energy level A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The t ...
. Such inelastic scattering reduces the energy (or increases the wavelength) of the outgoing beam. Inelastic scattering is useful for probing such electron excitation, but not in determining the distribution of atoms within the crystal. Longer-wavelength photons (such as
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
) would not have sufficient resolution to determine the atomic positions. At the other extreme, shorter-wavelength photons such as
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 ...
s are difficult to produce in large numbers, difficult to focus, and interact too strongly with matter, producing particle–antiparticle pairs. Similar diffraction patterns can be produced by scattering electrons or
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the atomic nucleus, nuclei of atoms. Since protons and ...
s. X-rays are usually not diffracted from atomic nuclei, but only from the electrons surrounding them.


Interference

X-ray interference is the addition ( superposition) of two or more X-ray
wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (re ...
s that results in a new wave pattern. X-ray interference usually refers to the interaction of waves that are correlated or
coherent Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deriv ...
with each other, either because they come from the same source or because they have the same or nearly the same
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
. Two non-
monochromatic A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochro ...
X-ray waves are only fully
coherent Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deriv ...
with each other if they both have exactly the same range of
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
s and the same phase differences at each of the constituent wavelengths. The total phase difference is derived from the sum of both the path difference and the initial phase difference (if the X-ray waves are generated from two or more different sources). It can then be concluded whether the X-ray waves reaching a point are ''in phase'' (constructive interference) or ''out of phase'' (destructive interference).


Technologies

There are a variety of techniques used to funnel X-ray photons to the appropriate location on an X-ray detector: * Grazing incidence mirrors in a
Wolter telescope A Wolter telescope is a telescope for X-rays that only uses grazing incidence optics – mirrors that reflect X-rays at very shallow angles. Problems with conventional telescope designs Conventional telescope designs require reflection or refract ...
, or a Kirkpatrick–Baez X-ray reflection microscope. *
Zone plate A zone plate is a device used to Focus (optics), focus light or other things exhibiting wave character.G. W. Webb, I. V. Minin and O. V. Minin, “Variable Reference Phase in Diffractive Antennas”, ''IEEE Antennas and Propagation Magazine'', ...
s. * Bent crystals. * Normal-incidence mirrors making use of multilayer coatings. * A normal-incidence lens much like an
optical lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
, such as a compound refractive lens. * Microstructured optical arrays, namely, capillary/polycapillary optical systems. *
Coded aperture Coded apertures or coded-aperture masks are grids, gratings, or other patterns of materials opaque to various wavelengths of electromagnetic radiation. The wavelengths are usually high-energy radiation such as X-rays and gamma rays. By blocking ra ...
imaging. * Modulation collimators. * X-ray waveguides. Most X-ray optical elements (with the exception of grazing-incidence mirrors) are very small and must be designed for a particular incident angle and energy, thus limiting their applications in divergent
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
. Although the technology has advanced rapidly, its practical uses outside research are still limited. Efforts are ongoing, however, to introduce X-ray optics in medical
X-ray imaging Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
. For instance, one of the applications showing greater promise is in enhancing both the contrast and resolution of mammographic images, compared to conventional anti-scatter grids. Another application is to optimize the energy distribution of the X-ray beam to improve contrast-to-noise ratio compared to conventional energy filtering.


Mirrors for X-ray optics

The mirrors can be made of glass, ceramic, or metal foil, coated by a reflective layer. The most commonly used reflective materials for X-ray mirrors are
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
and
iridium Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density o ...
. Even with these the critical reflection angle is energy dependent. For gold at 1 keV, the critical reflection angle is 2.4°. The use of X-ray mirrors simultaneously requires: * the ability to determine the location of the arrival of an X-ray photon in two dimensions, * a reasonable detection efficiency.


Multilayers for X-Rays

No material has substantial reflection for X-rays, except at very small grazing angles. Multilayers enhance the small reflectivity from a single boundary by adding the small reflected amplitudes from many boundaries coherently in phase. For example, if a single boundary has a reflectivity of ''R'' = 10−4 (amplitude ''r'' = 10−2), then the addition of 100 amplitudes from 100 boundaries can give reflectivity ''R'' close to one. The period Λ of the multilayer that provides the in-phase addition is that of the standing wave produced by the input and output beam, Λ = ''λ''/2 sin ''θ'', where ''λ'' is the wavelength, and 2''θ'' the half angle between the two beams. For ''θ'' = 90°, or reflection at normal incidence, the period of the multilayer is Λ = ''λ''/2. The shortest period that can be used in a multilayer is limited by the size of the atoms to about 2 nm, corresponding to wavelengths above 4 nm. For shorter wavelength a reduction of the incidence angle ''θ'' toward more grazing has to be used. The materials for multilayers are selected to give the highest possible reflection at each boundary and the smallest absorption or the propagation through the structure. This is usually achieved by light, low-density materials for the spacer layer and a heavier material that produces high contrast. The absorption in the heavier material can be reduced by positioning it close to the nodes of the standing-wave field inside the structure. Good low-absorption spacer materials are Be, C, B, B4C and Si. Some examples of the heavier materials with good contrast are W, Rh, Ru and Mo. Applications include: * normal and grazing-incidence optics for telescopes from EUV to hard X-rays, * microscopes, beam lines at synchrotron and FEL facilities, * EUV lithography. Mo/Si is the material selection used for the near-normal incidence reflectors for EUV lithography.


Hard X-ray mirrors

An X-ray mirror optic for
NuStar NuSTAR (Nuclear Spectroscopic Telescope Array, also named Explorer 93 and SMEX-11) is a NASA space-based X-ray telescope that uses a Conical intersection, conical approximation to a Wolter telescope to focus high energy X-rays from astrophysics ...
space telescope working up 79 keV was made using multilayered coatings, computer-aided manufacturing, and other techniques.NuStar: Instrumentation: Optics
The mirrors use a
tungsten Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
/
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
(W/Si) or
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...
/ silicon-carbide (Pt/SiC) multicoating on slumped glass, allowing a
Wolter telescope A Wolter telescope is a telescope for X-rays that only uses grazing incidence optics – mirrors that reflect X-rays at very shallow angles. Problems with conventional telescope designs Conventional telescope designs require reflection or refract ...
design.


See also

* Kirkpatrick–Baez mirror *
X-ray telescope An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. In order to get above the Earth's atmosphere, which is opaque to X-rays, X-ray telescopes must be mounted on high altitude rockets, balloon ...
*
Wolter telescope A Wolter telescope is a telescope for X-rays that only uses grazing incidence optics – mirrors that reflect X-rays at very shallow angles. Problems with conventional telescope designs Conventional telescope designs require reflection or refract ...
, a type of X-ray telescope built with glancing-incidence mirrors *
XMM-Newton ''XMM-Newton'', also known as the High Throughput X-ray Spectroscopy Mission and the X-ray Multi-Mirror Mission, is an X-ray space observatory launched by the European Space Agency in December 1999 on an Ariane 5 rocket. It is the second cornerst ...
and
Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...
, orbiting observatories using X-ray optics *
X-ray spectroscopy X-ray spectroscopy is a general term for several spectroscopic techniques for characterization of materials by using x-ray radiation. Characteristic X-ray spectroscopy When an electron from the inner shell of an atom is excited by the energy o ...
,
X-ray photoelectron spectroscopy X-ray photoelectron spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique based on the photoelectric effect that can identify the elements that exist within a material (elemental composition) or are covering its surface, ...
,
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 ...


References


External links

* * {{cite web, title=X-ray optics, url=http://www.x-ray-optics.de/index.php/en/, access-date=19 November 2019, last=Arndt Last
Optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
Optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
Optics Radiography
Optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...