Radians’ Portability and Versatility Helps it Measure Nuclear Fusion Reactor


The Max Planck Institute in Germany is researching a revolutionary approach to energy generation: nuclear fusion. The plasma vessel where Max Planck will test its theories has a portal barely a foot wide. But the API Radian laser tracker can easily be mounted inside.

Industrial measurement systems in basic research areas

Very rarely is a research area as dependent on 3D-measurement technology in the set-up of its major experiments as fusion plasma physics. One thing is clear: without laser based metrology and their sisters-in spirit – 3D CAD software – the Wendelstein 7-X fusion research system that is close to completion in Greifswald could not have even been designed, let alone constructed, without laser trackers.

The plasma vessel, which is surrounded by hot plasma at up to 100 million degrees, is reminiscent of a twisted, half-deflated bicycle inner tube of approx. 11 m at the large diameter and approx 1,5 m at the small diameter. How can we determine the extent to which the actual vessel, made from 17-mm-thick special steel, deviates from the model created in the CAD? During the manufacture of the individual plasma vessel modules, the latter were accessible from the outside, and their contours could therefore be checked from the outside at the manufacturer’s site using a laser tracker.

On assembling the individual modules to form the complete vessel access from the outside is no longer possible. With the introduction of highly compact laser trackers that are not much larger than a shoebox and weigh less than 10 kg, it is now also possible to bring these devices into the plasma vessel through the narrow access opening of approx 800 x 400 mm cross-section, and to set them up there. In comparison to photogrammetry, the use of a laser tracker saves process time, and provides equivalent, or even somewhat more accurate measurement results.

The compactness of today’s laser trackers also offers an invaluable asset in another area. In the assembly and alignment of ports, for example. In order to be able to measure the pipe to be welded onto the plasma vessel, a laser tracker must be able to look into the approx. 2-metre-long port from the outside. The laser tracker is fitted to the support with appliances that have been specially designed for this purpose. Only in this way can measurements be carried out in the inside, and the pipe position be determined, which is what really matters. And the measurement system, which is normally mounted vertically on a stand, must be able to achieve its accuracy, even in the most oblique installation position.