Neutron Diffraction @ANSTO

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Neutron Diffraction _at_ANSTO

• Alison Edwards
• Bragg Institute ANSTO

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What to do when theres a nuclear reactor next
door
Assemble the best team of scientists, engineers
and tradespeople and build something to match!
www.ansto.gov.au/research/bragg_institute.html
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Diffraction what is it?

• Radiation interacting with matter where spacing
  between scattering centres is similar to the
  wavelength of the radiation
• If we have a suitable lens we can create a direct
  image

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The Mathematics

• Laue conditions White Beam experiment
  (discovery 1912, Nobel Prize 1914 Friedrich and
  Knipping were Laues students)
• l 2d sinQ (Lawrence Bragg early 20s, discovery
  1913 Nobel Prize 1915) monochromatic experiment
• Laue conditions stated first, but insoluble,
  Bragg equation is a valid solution

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Neutron Attenuation
idea and realization Heinz-Werner Schmitz, GKSS
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Neutron Diffraction instruments

• WOMBAT and ECHIDNA are powder diffractometers
• KOALA is a single crystal diffractometer
• KOWARI uses diffraction measurements to assess
  stress in objects
• The neutron was not discovered until
  1932(Chadwick, Nobel Prize 1935)

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Ewald Sphere
2q
Incident Beam
reciprocal lattice origin
q-2q scan
1/l
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Powder Diffraction

• Many tiny crystals
• Random orientations (we hope)
• Inherently 1-D data
• Suffers from overlap
• Resolution dependent on distance from crystal
• Do not need single crystals- microcrystalline
  powder will work well

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Single Crystal Diffraction

• Data inherently 3-Dimensional
• Problems can arise due to absorption and/or
  primary and seconday beam extinction
• Must have single crystal of suitable size
  minimum 0.1 mm3 ie 0.5 x 0.5 x 0.5 mm3

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A Laue Pattern

• Attribution to ILL needed

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Ewald Sphere
2q
Incident Beam
reciprocal lattice origin
q-2q scan
1/l
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Neutron scattering length and density
Neutron SLD (10-6 Å-2) ?(H2O) -0.56 ?(D2O)
6.36
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Better Than X-ray Vision ?...(Neutron
Radiography)
Penetrating ability of neutrons - sensitive to
nuclei such as boron and hydrogen
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Thank You