Simulation tool reveals stunning images of JET during a plasma

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How would a tokamak look during a fusion experiment if you could see all the way through to the hot plasma fuel inside it?

CCFE scientist Dr Alex Meakins has answered this question by creating a series of striking computerised images of the JET – the European fusion project based at Culham – rendered in glass.

The models, based on real design data from JET, demonstrate a new simulation tool known as CHERAB. Developed by Alex and colleagues at CCFE, CHERAB aims to speed up the generation of accurate data from fusion devices.

CHERAB combines plasma modelling with a powerful photo-realistic ray-tracer. Ray-tracing is a rendering technique for generating an image by tracing the path of light through a virtual world and predicting the effects of the light bouncing off objects.

CHERAB is being used by fusion scientists to simulate all sorts of visible and infrared plasma measuring tools, known as diagnostics. The diagnostic systems measure the light output of the plasma to study properties such as its temperature and density. Inferring these properties requires an accurate understanding of how the light is produced and bounces around inside the machine. The more accurately we can model these systems the more accurate our measurements of fusion plasmas will be.

A long-standing problem for fusion diagnostics has been reflections of light from the surfaces inside tokamaks. If they are not modelled, the reflections can interfere with the ability to make accurate plasma measurements. This is a particular problem for metal-walled devices such as JET and the future ITER machine. CHERAB solves this through its integration with a ray-tracer that can handle complex computerised wall models with realistic material properties.

CHERAB is being developed through a collaboration of diagnostic scientists and Research Software Engineers (RSEs). RSEs combine professional software engineering skills with an understanding of the research context. Alex Meakins, the RSE who developed the core of CHERAB, is a physicist and software engineer who has always worked on the boundary between these two fields.

He said: “We've placed a strong focus on making CHERAB robust and easy to expand by physicists of all skill levels. Using the tools CHERAB provides, physicists can rapidly assemble code to answer questions in days that would have previously taken months of custom development. The glass JET render was a fun demonstration of the flexibility of the system!"

The CHERAB software is open-source and is available on github at:

Click on the images to download them in full-size resolution. They make stunning 'Glass JET' wallpaper!

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