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X-Ray Monochromators

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

X-Ray Monochromators

The spectral analysis of X-rays emitted by a sample after irradiation. It is based on the following phenomenon: an atom relaxes after excitation by emitting X-ray radiations at specific wavelengths, which reveal the identity of the emitting species.

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

  • Crystal Monochromator
    Supplying a range of crystals for X-Ray Spectrometry: LiF, Quartz or SiO2, InSb, Si, Ge, PET, ADP, Beryl, TlAP, RbAP, KAP, and CsAP.  
  • Radiation Scintillation Detector
    A radiation detector in order to measure the intensity of the various spectral lines as singled out by the monochromator. The detector combining Nal(TI) or LaBr3, 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 the sample. A detector is used to measure the intensity of spectral lines singled out by the monochromator.

X-Ray Monochromator crystals can be supplied in the two following shapes:

  • Flat plates – supplied unmounted or mounted onto holders
  • Curved plates – supplied on tailor-made holders for use in instruments such as microprobes, scanning electron microscopes, Synchrotrons, XFEL, Plasma Physics.  

 

 

Uses/Applications

  • A monochromating crystal behaves in X-ray spectrometry similar to diffraction grating in optics. When rotated with respect to the incident polychromatic beam, the crystal will diffract at Theta angle from crystal lattice to 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 the 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 are: 

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).

We will offer the best 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. 

 
Scroll right for additional crystals →
Crystal Lithium fluoride Quartz Indium Antimonide Silicon Germanium Pentaerythritol PET Ammonium Dihydrogen Phosphate ADP Beryl Acid Phthalates Crystal
  Thallium TIAP Rubidium RbAP Potassium KAP Cesium CsAP  

Chemical Formula

 LiF SiO2 InSb Si Ge C(CH2OH2) NH4H2PO4 3BeO,Al2O36SiO2 CO2HC6H4CO2TI CO2HC6H4CO2Rb CO2HC6H4CO2K CO2HC6H4CO2Cs Chemical formula
Crystal system Cubic Hexagonal Cubic Cubic Cubic Quadratic Quadratic Hexagonal Orthorhombic Orthorhombic Orthorhombic Orthorhombic Crystal System
Parameters  

 

                         Parameters
a..................Å.... 4.027 4.913 6.48 5.431 5.658 6.16 7.530 9.21 6.63 6.55 6.46 6.580 a..................Å....
b..................Å....   4.913           6.16 7.530 9.21 10.54 10.02 9.61 10.752 b..................Å....
c..................Å....   5.405           8.74 7.542 9.17 12.95 13.06 13.33 12.825 c..................Å....
ß........................                               ß........................
Reflecting planes orientations (200) (220) (420) (1011) (1010) (111) (111) (220) (111) (220) (002) (101) (1010) (001) (001) (001) (001) Reflecting planes orientations
2d in Å  4.027 2.848 1.801 6.684 8.514 7.480 6.271 3.840 6.532 4.000 8.740 10.648 15.950 25.900 26.120 26.640 26.650 2d in Å
Usual surface finish Cleaved or Treated Treated Treated Polished Polished Polished Polished Polished Polished Polished Cleaved or Treated Polished or Treated Polished Cleaved Cleaved Cleaved Cleaved Usual surface finish
Reflectivity Intense Intense Average Good Good Intense Intense Average Intense Intense Intense Average Average Intense Intense Good Good Reflectivity
Calibration elements

Mo, Fe, Ti

 Mo, Fe Mo Cu Cu Si Cu Cu Cu Cu Al, Si Mg Mg Na, Mg Na Na Na Calibration elements
Common Applications From K to heavy elements Heavy elements
Lines splitting		 Heavy elements
Lines splitting		 As
Ge (111)		 As PET Quantitative analysis of silicon Extinction of even order spectral lines   Mg Na and following elements F to Al Na to Al, up to F in emission probes Na to Al, up to F in emission probes Na to Al, up to F in emission probes Common applications

 

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 X-Ray Monochromators
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