Scientists at the Max Planck Institute for Plasma Physics said the Wendlestein 7-X stellarator had broken its previously set record for temperature and plasma density on June 25, confirming its performance capabilities with upgraded components.
The facility in Greifswald, Germany, is the largest stellarator type plasma-producing fusion reactor in the world. It was first operational in 2015, but it has since been graphite tiles in the vessel walls that can withstand higher temperatures and longer plasma discharges, according to the institute's statement.
“With the so-called divertor it is also possible to control the purity and density of the plasma: The divertor tiles follow the twisted contour of the plasma edge in the form of ten broad strips along the wall of the plasma vessel. In this way, they protect particularly the wall areas onto which the particles escaping from the edge of the plasma ring are made to impinge. Along with impurities, the impinging particles are here neutralised and pumped off,” the institute said.
Plasma durations of six seconds were being attained in operations prior to the upgrades, but plasmas lasting up to 26 seconds are now being produced. “A heating energy of up to 75 megajoules could be fed into the plasma, this being 18 times as much as in the first operation phase without divertor,”
The heating power could also be increased, which is required in order to produce high plasma density.
The record: “At an ion temperature of about 40 million degrees and a density of 0.8 x 1020particles per cubic metre Wendelstein 7-X has attained a fusion product affording a good 6 x 1026 degrees x second per cubic metre, the world’s stellarator record. “This is an excellent value for a device of this size, achieved, moreover, under realistic conditions, i.e. at a high temperature of the plasma ions”, said the facility's Professor Sunn Pedersen.
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