Crystal monochromator
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A crystal monochromator is a device in neutron and X-ray optics to select a defined wavelength of the radiation for further purpose on a dedicated instrument or beamline.[1] It operates through the diffraction process according to Bragg's law.
Similar devices are called crystal analyzer for the examination of scattered radiation.
Crystal Monochromator
[edit]A crystal monochromator is an optical device used in X-ray and neutron spectroscopy to isolate a specific wavelength or a narrow range of wavelengths from a broader spectrum of radiation. It operates based on the principle of diffraction through a crystalline structure, governed by Bragg's Law. Crystal monochromators are integral to applications in materials science, structural biology, and high-energy physics.
Principles of Operation
[edit]Crystal monochromators utilize the atomic lattice structure of a crystal to diffract incident radiation at specific angles. The diffraction condition is defined by Bragg’s Law: nλ=2dsinθ Where:
- n: Order of diffraction,
- λ: Wavelength of the incident radiation,
- d: Spacing between atomic planes in the crystal,
- θ: Angle of incidence.
By adjusting the angle of the crystal, the monochromator selectively allows radiation of a desired wavelength to pass while filtering out others.
Materials
[edit]Commonly used materials for crystal monochromators include:
- Silicon (Si): Offers high purity and stability, ideal for synchrotron radiation.
- Germanium (Ge): Suitable for specific wavelength ranges due to its lattice properties.
- Quartz: Used for its thermal stability in certain applications.
These materials are chosen for their well-defined crystal lattice structures and their ability to withstand the operational environment.
Configurations
[edit]Crystal monochromators can be designed in various configurations:
- Flat Crystal Monochromators: Use a single, flat crystal to diffract radiation. They are simple and commonly employed in laboratory X-ray setups.
- Double-Crystal Monochromators: Consist of two crystals aligned to improve wavelength purity and minimize beam divergence.
- Bent Crystal Monochromators: Use curved crystals to focus the diffracted beam, enhancing intensity and resolution.
Applications
[edit]Crystal monochromators are widely used in scientific and industrial research:
- X-ray Diffraction (XRD): To study the atomic and molecular structure of materials.
- Synchrotron Beamlines: For producing monochromatic X-rays in synchrotron radiation facilities.
- Neutron Scattering: To isolate specific neutron wavelengths for scattering experiments.
- Spectroscopy: In high-resolution X-ray and neutron spectrometers to filter out unwanted wavelengths.
References
[edit]- ^ Streli, Christina; Wobrauschek, P.; Kregsamer, P. (2017-01-01), Lindon, John C.; Tranter, George E.; Koppenaal, David W. (eds.), "X-Ray Fluorescence Spectroscopy, Applications", Encyclopedia of Spectroscopy and Spectrometry (Third Edition), Oxford: Academic Press, pp. 707–715, ISBN 978-0-12-803224-4, retrieved 2024-11-09
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