Materials engineering for fusion energy frequently matures along two paths simultaneously. High-heat flux facilities provide qualifications that the candidate material can survive the power it will receive, and tokamaks demonstrate the feasibility of that material in the fusion plasma environment.
In newly published work from S.H. Messer and colleagues, the fusion plasma exhaust in DIII-D was directed into the Small Angle Slot (SAS) divertor region. The narrow geometry of this wall shape is expected to help contain high-Z materials, such as the tungsten coated on the divertor tiles for this experiment. The research team observed how tungsten escapes this closed geometry as a function of the magnetic field parameters (which set particle drift directions).
The “holiday kaleidoscope” graphic is chosen not just for whimsy, but to highlight the broad coverage of a detector array that measures low energy x-rays emitted by the plasma. By measuring a specific energy range, this diagnostic system can determine the density of tungsten across the plasma interior. In the ideal plasma scenario, the tungsten protecting the divertor tiles will stay in the divertor and not escape to pollute the hot, fusing plasma core.
This work was led by the University of Tennessee, Knoxville, with co-authors from Fusion and Fission at ORNL, General Atomics, University of Toronto, UC San Diego, and Sandia National Laboratories.
S.H. Messer, et al., Nuclear Materials and Energy 38, 101566 (2024), https://doi.org/10.1016/j.nme.2023.101566
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