APREX TRACK R&D meets the challenge of magnetic fusion turbulence
 
Crosses represent the center of mass of structures, obtained with APREX TRACK R&D. The red curve depicts the position of the last closed magnetic flux surface. The video has been recorded at a frame rate of 270.000 frames per second.

The research on magnetic fusion aims to develop a new type of nuclear power plant by reproducing, in a plant, thermonuclear reactions which take place in the sun. Confining a star in a box is all but an easy task. Nevertheless, thousands of scientists around the world work hard to achieve this goal, because nuclear fusion would enable massive energy production from water, with very limited nuclear wastes compared to today’s nuclear power plants based on nuclear fission. In a fusion reactor, the temperature drops from several millions of degrees in the plasma core, where the fusion reactions take place, to about a thousand degrees on the reactor’s inner wall. This situation generates turbulence, in a similar way as what happens in a kettle, except that in a fusion device the turbulence is so strong that it can stop fusion reactions. Therefore, understanding turbulence in fusion devices is one of the key issues on the path towards the production of electricity by fusion power plants.

Combined with a tomographic reconstruction algorithm, APREX TRACK R&D is used to identify, track and characterize turbulent structures recorded by fast framing cameras. Given the very complex dynamics of turbulent structures and their short lifetime (typically 20 microseconds), their automatic tracking is extremely challenging.

The APREX TRACK software is the first solution which has proved to achieve efficient tracking under these conditions. The automatic processing enables a fast and complete analysis of full records in poor light conditions (no external gas puff was used to enhance the Signal-to-Noise ratio). The individual motion of turbulent structures is well reconstructed, without the need to use conditional averaging techniques, which opens wide perspectives for a better understanding of turbulence in fusion devices. Results obtained by an international team (Czech Republic, France, United Kingdom) on the COMPASS tokamak (IPP Prague) have just been published in the latest issue of Nuclear Fusion: https://doi.org/10.1088/1741-4326/ab0d4c

 

 

– Sequence of 10 frames (false colors) showing positive turbulent structures (so-called “blobs”, in yellow) and negative structures (density holes, in dark blue) in the edge of the COMPASS tokamak. Crosses represent the center of mass of structures, obtained with APREX TRACK R&D. The red curve depicts the position of the last closed magnetic flux surface. The video has been recorded at a frame rate of 270.000 frames per second.