Measuring protective tiles in an experimental fusion device

Third Dimension
29 October 2008

 

JET is the world's largest nuclear fusion power experiment and is funded by the European Fusion Development Agreement (EFDA) with the intention of furthering development in power generation through nuclear fusion. Based in Culham, UK, the project commenced in 1983 and is at the absolute cutting edge in terms of scientific development.

The tokomak (that is, the device that is central to the concept of nuclear fusion power generation) has a heating capacity of around 40 Megawatts. In order to achieve power generation through nuclear fusion, plasma temperatures of over 100 million degrees Kelvin are required. This means that it is critical that all components of the tokomak are as perfectly engineered as current technology will allow.

Part of the process of the ongoing improvement of the project has been to upgrade the protective tiles that line the tokomak core to allow the greater capacity that has been added to the device. As such, the tiles are now being replaced with a new design that is composed of a carbon-fibre composite with beryllium coating.

Tiles are of a size of around 1 square cm and are densely packed to cover the inner area of the tokomak core. The tiles are slightly offset at an angle which encourages the plasma in the core to circulate in a controlled manner. However, this also presents a challenge in ensuring that the tiles are within a strictly controlled tolerance band. Any excessive amount of step or gap between tiles increases the danger of contamination from the plasma, which could cause tiles to detach meaning replacement would be required.

Consequently, ensuring that the tiles are correctly manufactured prior to install (and measuring them to ensure they are still usable after an experiment) is extremely important. There are thousands of tiles in the device (the area covered is around 20 sq-m), so such measurement also have to be conducted quickly and if necessary, whilst installed. This means that the only feasible way to do so is with a handheld measurement device. Until now, the required level of repeatability has not existed on any device available on the market.

Third Dimension was able to offer a super high resolution GapGun as a solution to JET. Whilst the typical resolution of this device is typically 10µ, this has been reduced further for step measurements through a combination of hardware and software improvements. This means that initial results have indicated real world repeatability results of as little as 3µ.

This means that not only is it possible to reduce the amount of tiles that fail during experiments (allowing for a higher chance of successful tests), but that in the future it could also be possible to make even tighter tolerances. This in itself could potentially improve the development of fusion technology meaning a commercially available fusion device could be a reality even sooner.

 

This is the abstract of a presentation given at the 2008 LVMC.  To see a PDF of the presentation material, click here.

 

© 1995 - Third Dimension. All Rights Reserved