Research enhances performance of Germany's new fusion device

PPPL-led research enhances performance of Germany's new fusion device
Five superimposed images of W7-X magnetic surfaces displaced by changes in application of trim coil currents. Credit: Max Planck Institute of Plasma Physics

A team of U.S. and German scientists has used a system of large magnetic "trim" coils designed and delivered by the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) to achieve high performance in the latest round of experiments on the Wendelstein 7-X (W7-X) stellarator. The German machine, the world's largest and most advanced stellarator, is being used to explore the scientific basis for fusion energy and test the suitability of the stellarator design for future fusion power plants. Such plants would use fusion reactions such as those that power the sun to create an unlimited energy source on Earth.

The new experiments amply demonstrated the ability of the five copper trim coils and their sophisticated control system, whose operation is led on-site by PPPL physicist Samuel Lazerson, to improve the overall performance of the W7-X. "What's exciting about this is that the trim coils and Sam's leadership are producing scientific understanding that will help to optimize future stellarators," said PPPL physicist Hutch Neilson, who oversees the laboratory's collaboration on the W7-X with the Max Planck Institute of Plasma Physics, which built the machine and now hosts the international team investigating the behavior of plasmas confined in its unique magnetic configuration.

Stellarators are twisty, doughnut-shaped facilities whose configuration contrasts with the smoothly doughnut-shaped facilities called tokamaks that are more widely used. A major advantage of stellarators is their ability to operate continuously with low input power to sustain the plasma without plasma disruptions—a risk that tokamaks face—enabling the facilities to operate efficiently in steady state. A disadvantage is that the twisting geometry is more complex to design and build.

The W7-X completed its second round of experiments in December with improved heating and measurement capabilities. A special feature of the second round was its use of an "island divertor" to exhaust heat and particles leaving the plasma. This important tool consists of a chain of specially shaped magnetic fields at the edge of the plasma intersected by 10 divertor plates. Any deviation of these fields from their designed configuration can cause the divertor plates to overheat and limit the performance of the plasma.

The recent experiments demonstrated the ability of the trim coils to measure and correct such deviations, which are known as "error fields." Controlling such fields at the edge of the plasma enabled the W7-X to produce plasma discharges lasting up to 30 seconds. "The trim coils have proven extremely useful, not only by ensuring a balanced exhaust onto the divertor plates, but also as a tool for the physicists to perform magnetic field measurements of unprecedented accuracy," said Thomas Sunn Pederson, Max Planck director of stellarator edge and divertor physics.

Achieving the control required the trim coils to perturb the magnetic field in a way that made clear the size of the error . Complementary experiments by Lazerson and Max Planck scientist Sergey Bozhenkov then confirmed predictions of the needed power of the trim coils to correct the deviations—an amount that equaled just 10 percent of the full power of the coils. "The fact that we only required 10 percent of the rated capacity of the trim coils is a testament to the precision with which W7-X was constructed," Lazerson said. "This also means that we have plenty of trim capacity to explore divertor overload scenarios in a controlled way.

Explore further

Physicists confirm the precision of magnetic fields in the most advanced stellarator in the world

Citation: Research enhances performance of Germany's new fusion device (2018, March 29) retrieved 24 April 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Mar 29, 2018
This is so cool! Fusion will get here, it's just a matter of discovering the pieces of the puzzle and assembling them.

Mar 29, 2018
I hope you're right. People have been saying things like that for the last 50 years.

Mar 30, 2018
Fusion, like really good batteries will never get here.

Mar 30, 2018
When the scientists understand the order of the process of forming particles of matter and see how the subatomic particles form and from them all the chemical elements, then they will see that their process is contrary to the natural laws of obtaining energy. How and from what is formed the helium atom, and whether there is energy and how.?

Mar 30, 2018
Energy is neither created or destroyed

The energy required to heat and compress the hydrogen to form helium is the energy given up when hydrogen forms helium. In practice 100% efficiency is unobtainable because of heat loss in the reactor. The reactor temperature is millions of degrees centigrade, there is no known material that can stand this temperature plus the neutrons necessary to carry the heat of fusion away are highly radioactive bonding in the reactors structure destroying the material. A pipe dream is not even close!

Mar 30, 2018
You cannot take 30% of the heat of fusion away because fusion release's the energy of fusion which is required to fuse hydrogen into helium!

The Sun works; firstly it is an 800thousand mile diameter ball, it compress with gravity, the photons take millions of years to travel to the surface and leave the photosphere and only a miniscule percentage of the heat is lost which is immediately made because the sun cools and gravity compress's the sun where it heats up and expands release's photons and the process repeats which is sun oscillating every 11 years.

Mar 31, 2018
The Irony, magnets powered by Giga watt fossil fuelled power keep fusion fires burning.

only a miniscule percentage of the heat is lost which is immediately made because the sun cools and gravity compress's the sun where it heats up and expands release's photons and the process repeats which is sun oscillating every 11 years.

Apr 03, 2018
There is no excess heat, all the heat of fusion goes back into the reactor to fuse hydrogen and fosil fuel generators make up heat loss in the reactor. An interesting academic exercise in fosil fuel use!
This is where AI will prove its worth and wipe the floor with anything we can do - it could understand all the magnetic forces to get a functional and useful fusion reactor design.

Has anyone thought what to do with the excess heat - its obviously too hot to use the old tried and true hot water exchange to move a generator trick we have for years. Its fine and all fusing two atoms, and keeping it going - but making it usable is something else again.

Apr 04, 2018
The "liquid" state of matter is transformed into energy (heat, radiation, motion), and these are free gluons. Science has not yet realized it and spends millions of dollars in cash, in vain.
To ask me, this problem would be resolved in a very short time, only the science of today's understanding of the universe had to go to the "black hole" and transform it back to where it was headed, which is knowledge of the structure of the universe and the acceptance of the Spiritual Entity's respect of the universe.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more