Neutron Scattering

ANSTO Neutron Guide Hall

Neutron scattering techniques permit scientists to explore the structure and dynamics of materials under different conditions at atomic or molecular levels.

Neutrons are ideal for research in fields such as materials science and engineering, physics, chemistry, earth science and biology.

Neutrons produced in the core of ANSTO’s OPAL research reactor are directed through highly shielded, precision-engineered guide tubes to research targets in a series of instruments. When these neutrons strike target materials in the instruments they scatter, producing distinctive patterns that deliver information to researchers.

Neutrons are non-destructive, and can penetrate deeply into materials. By directing them to reflect at low angles from the surfaces of targets, information can also be gained on the properties of the surface, or the layers of the target’s structure. Two types of neutrons are produced in the OPAL research reactor for scientists’ use.

By varying their temperature, they can be tuned to different wavelengths to make investigations over sizes ranging from a single atom to a molecule that could comprise hundreds, or thousands, of atoms. This means they can be used to “see” different structures in materials.

Thermal and cold neutrons

Most neutrons produced by OPAL are thermal neutrons. They emerge from the beam tubes transporting them from the core of the reactor at about 45-50 degrees Celsius. OPAL is also able to make cold neutrons which are ideal for looking at organic matter at the molecular level. Before entering the beam tubes, on the way to research targets, they are chilled by passing them through a reservoir of 20 litres of liquid deuterium at almost minus 250 degrees Celsius.

ANSTO's neturon beam instruments
 

ANSTO currently has a suite of seven of neutron beam instruments named after Australian fauna (below). A comprehensive brochure on these instruments can be found here. An additional three instruments, also named after Australian fauna, TAIPAN PELICAN SIKA and KOOKABURRA are under construction. A further three instruments (BILBY, DINGO and EMU were approved in the 2009 Commonwealth budget).

Echidna – high resolution powder diffractometer

Echidna can be used to determine structures of newly created materials, to better understand their properties. For example, it could be used to investigate bulk samples or samples in extreme environments (pressure, temperature, stress, magnetic and electric fields, or combinations of these). Relevant fields include solid-state physics, materials science, chemistry, geoscience, and engineering.

Koala - Quasi-Laue diffractometer

The diffraction patterns created when neutrons hit a sample will allow scientists to determine the location of atoms within its crystalline structure, providing data about its precise structure and its properties. Applications will include the development and study of new pharmaceuticals, modern synthetic chemistry, and advanced materials.

Kowari – Residual stress diffractometer

This is a non-destructive method applicable to nearly all crystalline materials, providing sub-surface information not obtainable by any other technique. Kowari can be used to reveal residual stresses in welds such as rails, pipelines and airplanes; as well as stress corrosion or cracking in extreme environments.

Platypus – Time-of-flight neutron reflectometer

Neutron reflectometry, with the precision of a few atoms, provides information on the composition, changes in surface characteristics over time, thickness and interfacial roughness of thin films.

Relevant fields include study of soft matter in biological and chemical science and the study of thin-film magnetic devices to be used in future generations of computers.

Quokka – Small angle neutron scattering

SANS is a powerful technique for looking at structures on the nanoscale from 1 (one-billionth of a metre) to several hundred nanometres. Materials routinely characterised include alloys, ceramics, biological materials, colloidal materials, complex fluids, polymers, surfaces and interfaces and flux lattices in superconductors.

SIKA - Triple-axis spectrometer

SIKA is funded by the National Science Council Taiwan and will be operated by the Center for Neutron Beam Applications at the National Central University of Taiwan.

Triple-axis spectrometers use inelastic neutron scattering spectroscopy to measure excitations in materials. This gives the most detailed information on dynamical properties for crystalline materials available as single crystals.

Taipan - triple-axis spectrometer

Information gained in triple-axis spectrometers includes how materials change structure, and thermodynamic properties of solids. An application is the study of superconductors some of the most powerful electromagnets known, including those used in magnetic resonance imaging machines.