Neutron Alison Edwards Bragg Institute – ANSTO

What to do when there’s a nuclear reactor next door… Assemble the best team of scientists, engineers and tradespeople and build something to match!

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

The Mathematics Laue conditions “White Beam” experiment (discovery 1912, Nobel Prize 1914 Friedrich and Knipping were Laue’s students)  = 2d sin  (Lawrence Bragg early 20s, discovery 1913 Nobel Prize 1915) monochromatic experiment Laue conditions stated first, but insoluble, Bragg equation is a valid solution

Neutron Attenuation idea and realization: Heinz-Werner Schmitz, GKSS

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)

Ewald Sphere Incident Beam 1/ 22  -2  scan reciprocal lattice origin

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

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 mm 3 ie 0.5 x 0.5 x 0.5 mm 3

A Laue Pattern Attribution to ILL needed

Ewald Sphere Incident Beam 1/ 22  -2  scan reciprocal lattice origin

Neutron scattering length and density Neutron SLD (10 -6 Å -2 )  (H 2 O) = -0.56;  (D 2 O) = 6.36

Better Than X-ray Vision ?... (Neutron Radiography) Penetrating ability of neutrons - sensitive to nuclei such as boron and hydrogen

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