grazing incidence


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Related to grazing incidence: Glancing angle

grazing incidence

X-rays reflect from surfaces for the same physical reason that light reflects, mainly due to coherent scattering in the surface material. However, since X-ray photon energies are large, the refractive index, n, is slightly less than unity and reflection occurs only up to a critical angle, θ, where cos θ = n. The angle θ is usually small and thus X-ray reflection is only high for rays that graze the surface; hence ‘grazing incidence’. For example θ is about 1° for a gold surface and X-rays of wavelengths of about 0.3 nm (4 keV). θ is proportional to X-ray wavelength and also increases with the atomic number of the reflecting surface.

The space station Skylab was the first space mission to carry a large grazing incidence X-ray telescope, in fact two, both of which produced many high-resolution X-ray images of the solar corona in 1973–74. With two coaxial reflectors (usually a paraboloid/hyperboloid pair), high-quality X-ray images are produced over a field of view of order of the grazing angle. The great potential of such optical systems for cosmic X-ray astronomy was first demonstrated with the flight of a 60-cm diameter grazing incidence telescope on the Einstein Observatory in 1978–81. Subsequently, most X-ray astronomy satellites have employed or will employ this technique.

grazing incidence

[′graz·iŋ ‚in·sə·dəns]
(physics)
Incidence at a small glancing angle.
References in periodicals archive ?
However, grazing incidence wide-angle X-ray scattering measurements revealed some significant differences on the molecular level.
2])] for NS1 and NS2 increase in the whole range, while the values for TS1, TS2, ST1, ST2, TCS1, TCS2 first decrease and then increase to attain maximum value at grazing incidence.
Note that the reflection coefficients under the grazing incidence condition in (19) are in a slightly different form than the general Fresnel reflection coefficients given in text books such as [28].
9) For the 3[degrees] grazing incidence geometry that was used here, the information depth is about half a micron.
Diffraction at grazing incidence from surfaces, and reflectivity.
Therefore, there is no field below the ground plane and the field above the ground plane is doubled in the case of grazing incidence.
UCSD has demonstrated a grazing incidence final optic mirror with high damage threshold.
The researchers had to figure out the right grazing incidence geometry to reduce background noise, then how to make an electrochemical cell that was compatible with x-rays.
The system features the state-of-the-art technology, including the capability to perform in-plane grazing incidence diffraction (IP-GID).
Because X-rays can penetrate matter, the mirrors rely on what scientists refer to as grazing incidence optics.
The structural ordering in the casted layers of P3HT: PCBM was further verified using GI-XRD measurements employed at a grazing incidence angle of 0.