An ANSTO particle accelerator that has been used to authenticate Tom Roberts paintings, analyse ancient artefacts and detect trace amounts of pollutants has reached an important milestone.
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| The Van de Graaff accelerator has notched up more than 100,000 hours of operation. |
The Van de Graaff accelerator has notched up more than 100,000 hours of operation. Researchers from universities around the country gathered at ANSTO to mark the occasion.
At 35 years of age, the accelerator is long in the tooth, says Dr David Cohen, of ANSTO's Physics Division. "Van de Graaff accelerators are often pensioned off long before they reach that age but this one is still very useful," he says.
The instrument was bought in the early 1960s for 100,000 pounds by Dr John Symonds, then Physics Division Chief of ANSTO's predecessor, the Australian Atomic Energy Commission. It was used initially to complement the HIFAR nuclear research reactor in neutron studies.
More recently, the granny Van de Graaff has branched out into more applied areas such as art, archaeology, environmental science and conservation biology. Its strength is that it can be used to identify elements in amounts as low as a few parts per million without destroying the sample. One of the accelerator's main triumphs was the authentication of Tom Roberts paintings owned by the Australian Museum. It has also shed light on the rock art of the first Australians and ancient pottery from around the world.
It was used to trace the obsidian trade routes of Melanesia. Another major application was the identification of particles in atmospheric pollution. The particles have been implicated in respiratory illness.
ANSTO, in collaboration with CSIRO, has characterised pollution in the major cities of Australia, New Zealand and Southeast Asia, and pinned down the sources. The work is helping governments frame policies to clean up the air.
ANSTO, in collaboration with CSIRO, has characterised pollution in the major cities of Australia, New Zealand and Southeast Asia, and pinned down the sources. The work is helping governments frame policies to clean up the air.
The Van de Graaff has also found applications in occupational health and safety. From analysis of hair, scientists were able to gauge the levels of trace metals in the bodies of staff exposed to workplace toxins.
It has also been used to work out the metabolic rates of threatened animals, including lizards and possums of the West Australian deserts by analysing their blood. The work, aimed at determining the animals food requirements, has helped in the development of conservation strategies. ANSTO, often in collaboration with university scientists, uses the accelerator in several analytical techniques.
In one, dubbed PIXE (proton-induced x-ray emission), the Van de Graaff produces a beam of energetic protons (hydrogen nuclei) which is trained on the sample, says Dr Grahame Bailey, who runs the facility.
"The protons excite the outer atomic electrons of the sample, and knock some of them out of their normal orbits," Dr Bailey explains. The excited electrons lose their excess energy in the form of x-rays, the energy of which betrays the elements in the sample. The intensity of the x-rays indicates the concentration of the elements.
In another - PIGME (proton-induced gamma-ray emission) a beam of protons excites the nuclei of the atoms in the sample. The nuclei lose their energy in the form of radiation called gamma rays. Again, the energies and intensities reveal the composition of the material.
Physics Division Director, Dr Claudio Tuniz, says ANSTO and the Australian Institute of Nuclear Science and Engineering plan to replace the instrument with a small modern tandem accelerator. The new facility, with capabilities in both ion beam analysis and radiocarbon dating, will expand ANSTOs capabilities in environmental science, occupational health and industrial research.
Published: 14/05/1999