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  • A world in itself

    From a height of some 50 metres, you have the entire ITER worksite at your feet. The long rectangle of the Diagnostics Building stands out in the centre, with [...]

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  • US completes toroidal field deliveries for ITER

    The US Domestic Agency achieved a major milestone in February by completing the delivery of all US-supplied toroidal field conductor to the European toroidal fi [...]

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  • Thin diagnostic coils to be fitted into giant magnets

    Last week was marked by the first delivery of diagnostic components—Continuous External Rogowski (CER) coils—from the European Domestic Agency to the ITER Organ [...]

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  • Addressing the challenge of plasma disruptions

    Plasma disruptions are fast events in tokamak plasmas that lead to the complete loss of the thermal and magnetic energy stored in the plasma. The plasma control [...]

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  • Blending (almost) seamlessly into the landscape

    Located in the foothills of the French Pre-Alps, the ITER installation blends almost seamlessly into the landscape. The architects' choice ofmirror-like steel c [...]

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Of Interest

See archived articles

Fusion on the micro-scale

-Florian Aigner, Vienna University of Technology

Artur Golczewski from the Vienna University of Technology mounting the high precision scale. Photos (2): Vienna University of Technology (Click to view larger version...)
Artur Golczewski from the Vienna University of Technology mounting the high precision scale. Photos (2): Vienna University of Technology
One of the world's most accurate scales is currently being used for fusion research at the Institute of Applied Physics at the Vienna University of Technology (VUT). A research group led by Professor Aumayr reproduces the physical conditions on the fusion reactor's walls in its experiments. In the laboratory, the interaction between high-energy ions and solid surfaces can be studied much more precisely than it ever could inside an actual fusion reactor.

A key tool for this research is the quartz crystal microbalance, which was developed by Professor Michael Schmid from the VUT. A small piece of the surface material, which is supposed to be used in the fusion reactor, is irradiated with high-energy particle beams, and tiny changes of its weight are measured with great accuracy. This way, one can determine whether the particle bombardment knocks atoms out of the surface, reducing the mass of the specimen, or whether the incident particles are instead implanted into the material, thereby increasing its mass.

The vacuum chamber in which the high-precision measurements with the quartz crystal scale are being performed. (Click to view larger version...)
The vacuum chamber in which the high-precision measurements with the quartz crystal scale are being performed.
The microscale developed at VUT is one of the world's most accurate scales. "Mass changes of as little as one billionth of a gram can be measured," says Katharina Dobes, research assistant at the Institute of Applied Physics. Even if the particle bombardment only removes one single atomic layer from the surface, the resulting change in mass can still be evaluated.
The fundamental idea behind this incredible precision is rather simple: a quartz crystal is vibrated and its resonance frequency is measured. This frequency depends very sensitively on the crystal's mass. If the crystal surface is coated with the material under investigation and then hit by particles, the changing resonance frequency of the crystal can be translated in a mass change of the material on top of it. That way it is possible to determine the effect the particle bombardment has on the surface.

The application of this measuring device is not restricted to fusion research. "In particle-surface interactions, there are many quantum mechanical phenomena which play a crucial role. In this field, many interesting fundamental questions are yet to be answered," Professor Aumayr believes.


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