11/30/2021

Diffracted Rays

  1. X-ray Diffraction (XRD) The atomic planes of a crystal cause an incident beam of X-rays to interfere with one another as they leave the crystal. The phenomenon is called X-ray diffraction. Incident beam diffracted beam film crystal Effect of sample thickness on the absorption of X -rays.
  2. Introduction to Crystallography and X-Ray Diffraction Theory Diffraction occurs when light is scattered by a periodic array with long-range order, producing constructive interference at specific angles. The electrons in an atom coherently scatter light.

Overview of Instruments at the MIT CMSE XRD Facility

Conditions Required for X-Ray Diffraction Total intensity of the scattered (diffracted) X-rays from an atom at a specific scattering angle is less than the theoretical intensity of X-rays generated by the electrons The reason is absorption (fluorescence) of some of the diffracted X-rays by electrons at suitable positions around the atom. Diffraction of an X-ray beam by a crystalline solid is analogous to diffraction of light by droplets of water, producing the familiar rainbow. X-rays are diffracted by each mineral differently, depending on what atoms make up the crystal lattice and how these atoms are arranged.

PANalytical X'Pert PRO XRPD

The X'Pert is our workhorse powder diffractometer. It is normally kept in Bragg-Brentano geometry with a high-speed linear detector, which gives rapid high-quality XRD data from polycrystalline samples. We also have several accessories for this instrument, including a furnace for in-situ high temperature measurements, a cryostat for in-situ low temperature measurements, and a 15-position automatic sample changer.

Rigaku SmartLab Multipurpose Diffractometer

The Rigaku SmartLab is our 'Swiss Army Knife' of tools. It is capable of performing most common XRD measurements as well as many uncommon ones, and can be rapidly switched between various optical configurations including both Bragg-Brentano and Parallel-Beam geometries. It gives very good X-ray reflectivity (XRR) and grazing incidence XRD (GIXD) results. It also features a rotating anode X-ray source, which produces a high intensity beam. Because of its flexibility, most users can collect useful data on this instrument, but we especially recommend it for users who will be studying polycrystalline or epitaxial oxide thin films.

We have many accessories available for the SmartLab, including various optics, a linear detector, both incident-beam and diffracted-beam monochromators, a capillary stage, a furnace for in-situ measurements, a battery cell for lithium ion materials, and more. In addition, it has an in-plane arm which allows the detector to traverse more than a quarter sphere around a sample. With sample rotation, this allows it to collect full hemisphere in-plane reciprocal space maps (RSM) and in-plane pole figures.

Bruker Cobalt Source D8 Discover with GADDS

The General Area Detector Diffraction System (GADDS) posesses three unique capabilities that are not found in any of our other instruments:

  1. The source is Co instead of Cu, therefore, mitigating fluorescence from Fe and Co containing samples.
  2. A two-dimensional area detector, which captures more of the diffracted X-rays and facilitates study of materials that are textured, grainy, or under residual stress.
  3. Small beam spot size, used for micro-diffraction from very small samples, and capable of mapping across a sample.

The primary tradeoff is resolution, as diffraction peaks obtained from this instrument are very broad. This instrument is also capable of some basic transmission SAXS and GISAXS measurements.

Bruker D8 Discover HRXRD

Our High-Resolution X-ray Diffraction (HRXRD) instrument is primarily used for the study of epitaxial thin films. It is equipped with a 4-bounce germanium crystal monochromator, which strips nearly all unwanted radiation from the incident beam. The result is pure copper K-alpha1 radiation, which is needed for the analysis of things like lattice-matched materials on single crystal substrates. In addition, a linear detector is available to collect rapid reciprocal space maps (RSM). It is also capable of X-ray reflectivity (XRR) analysis of thin films. Because the monochromator also reduces the intensity of the X-ray beam, this instrument is not suitable for general purpose XRD on polycrystalline samples.

Bruker Tracer-III SD Handheld ED-XRF

Our X-ray fluorescence (XRF) unit provides rapid qualitative non-destructive elemental analysis. It is capable of identifying most elements heavier than magnesium in five minutes or less. Normally it gives qualitative results, e.g. trace element identification and relative comparisons of similar samples.

Rigaku Chromium Source RU-300 Rotaflex with D-Max/B XRPD

Rays

The RU-300 uses a high-power X-ray source along with a diffracted beam monochromator for rapid, high-quality data collection from polycrystalline samples. In addition, this instrument features a chromium anode, which is useful for reducing unwanted fluorescence from samples containing iron and cobalt. However, the goniometer and optics are limited: Your samples must be mounted vertically, and the instrument can only be used in Bragg-Brentano parafocusing geometry for polycrystalline materials.

Multiwire Laboratories Back-Reflection Laue Camera System

This instrument uses tungsten white radiation to rapidly find the orientation of single crystals. If you are interested in using the Laue system, please contact XRD staff.

Diffracted Rays For Sale

Bruker NanoStar SAXS

This hybrid instrument is composed of a Bruker NanoStar system for Small Angle X-ray Scattering (SAXS) on top of a Rigaku H3R rotating anode generator.

This system is currently under construction with no estimated completion date. When it is finished, we expect that it will produce high-quality transmission SAXS data in the 0 to 2 degree range.

Reflected And Diffracted Rays

SAXSLAB system

Diffracted Rays Diagram

This instrument is a dedicated small Angle X-ray Scattering with a Cu microfocus X-ray source, tunable collimation slits and a vacuum compatible DECTRIS PILATUS 300K detector.