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X-Ray Monochromators

X-Ray Monochromators

LiF, Quartz or SiO2, InSb, Si, Ge, PET, ADP, Beryl, TlAP, RbAP, KAP and CsAP

X-Ray Monochromators

For this spectral analysis, Saint-Gobain Crystals supplies two key components:

  • Monochromating Crystals
    Saint-Gobain Crystals supplies a whole range of X-Ray monochromators including LiF, Quartz or SiO2, InSb, Si, Ge, PET, ADP, Beryl, TlAP, RbAP, KAP and CsAP.  
  • Scintillation Detectors
    The detectors offered by Saint-Gobain Crystals combine a scintillating crystal (typically Nal(TI), LaCl3 (BrilLanCe 350) or LaBr3 (BrilLanCe 380)) directly coupled to a light sensing device with a low energy entrance window (Standard Detector Configurations - X-ray Detectors).

A monochromating crystal is used to disperse the various spectral components of the beam emitted by sample. A detector is used to measure intensity of spectral lines singled out by the monochromator.

Monochromating crystals can be supplied in the two following shapes:

  • Flat
  • Curved onto a holder

Flat crystals can be supplied unmounted or mounted onto holders. Saint-Gobain can provide standard or custom holders.  The curved crystals used in instruments such as microprobes, scanning electron microscopes, Synchrotrons, XFEL, Plasma Physics are always supplied on tailor-made holders.  

 

 

Uses/Applications

  • A monochromating crystal behaves in X-ray spectrometry similiar to diffraction grating in optics. When rotated with respect to the incident polychromatic beam, crystal will diffract at Theta angle from crystal lattice the spectral component at wavelength lambda along the direction that satisfies Bragg's law, namely: 2d sin(Theta) = n lambda, where integer n refers to the diffraction order.
  • Hence, the most important characteristic of a monochromating crystal is the double atomic spacing 2d, which gives the largest wavelength to be diffracted.
 

Features/Benefits

  • Standard orientations are offered with other orientations available on request. The standard orientation accuracy provided is 10 minutes with up to 1 minute accuracy possible.
  • Surface finish optimized for best intensity-resolution balance. The optimum finish depends on the specific case and strongly reflects the nature of the setup.

 

 

Two main types of focusing configurations may be considered: 

The Johann Geometry (semi-focusing)

A thin plate is produced by one of the two following methods:

  • Cleavage
  • Machining

The thin plate is then curved cylindrically and glued to a curved holder with approximate focusing.

The Johansson Geometry (exact focusing geometry)

 

Two different types of Johansson configurations, theoretically leading to perfect focusing, are considered:

  • Single machining Johansson
  • Double machining Johansson

The thin plate is either curved cylindrically, glued to a curved holder and one face is machined (single machining Johansson) or both faces are machined and then glued to a curved holder (double machining Johansson).

Saint-Gobain Crystals will choose the most appropriate technique according to the type of crystal, its dimensions and the radius of Rowland circle to be achieved. 

Other types of curvature may be investigated on request. Following designs can be made:

  • Logarithmic spiral
  • Elliptical
  • Conical
  • Parabolic
  • Sphere
  • Toroidal 

Manufacturing capabilities strongly depend upon the crystal nature, dimensions as well as the curvature radii. 

Related Documents

 X-Ray Monochromators
 Photonics Products Warranty