Breakthrough in superconducting materials opens new path to fusion

November 10, 2015
Conceptual design of the ARC fusion reactor. About the same size as the currently operating JET tokamak in the United Kingdom, but with three times the magnetic field strength, ARC is sized to produce 500 MW of deuterium-tritium fueled fusion power. Credit: Earl Marmar

In fusion reactor designs, superconductors (which suffer no resistive power loss) are used to generate the magnetic fields that confine the 100 million degree C plasma. While increasing magnetic field strength offers potential ways to improve reactor performance, conventional low-temperature superconductors suffer dramatic drops in current carrying ability at high magnetic fields. Now, the emergence of high-temperature superconductors that can also operate at high magnetic fields opens a new, lower-cost path to fusion energy.

A typical measure of fusion plasma performance is called "plasma beta," which is the ratio of plasma pressure to magnetic field pressure. Achieving a very high beta—generating the required plasma pressure with low magnetic field—could help reduce the cost of the superconducting magnets used in a fusion reactor. For this reason, many visions of fusion reactors try to maximize plasma beta at moderate magnetic field strengths. Operation at higher beta, however, pushes the plasma up against many performance limits, making plasma stability a tricky business.

But plasma beta is not the only consideration. Another ratio, the size of the confined plasma compared to the ion gyroradius, also determines overall energy confinement and dictates plasma performance. (The ion gyroradius is the helical path ions are forced to follow in the magnetic field.) Increasing decreases the ion gyroradius, which allows a reduction in the size of the fusion device with no loss of performance. This approach also lowers beta and the operates farther away from stability limits, in a "safe zone."

While scientists have explored both of these paths to improving performance, the recent development of the so-called "" opens a window for much higher magnetic fields, as the critical currents do not degrade rapidly, even at magnetic field values of 30 Tesla or higher. So these should really be called high-temperature, high-magnetic-field superconductors.

For tokamak design, the field strength limits are primarily determined by the maximum allowable stresses in the structural components holding the magnet together, and not by the intrinsic limits of the superconductors.

Even the most aggressive tokamak designs with conventional superconductor technology are limited to about 6 Tesla on-axis toroidal magnetic fields. By nearly doubling magnetic field strength, to about 10 Tesla on-axis, conceptual designs indicate that a tokamak approximately the physical size of the world's largest currently operating tokamak, JET, would be capable of producing 500 MW of power, and even net electricity. High-temperature, high-magnetic-field superconductors can also make it possible to incorporate jointed magnetic coils into the reactor design, dramatically improving flexibility, and ultimately, maintainability for reactor systems.

While several physics and technology challenges remain to be solved, the world-wide experience from tokamak experiments provides the basis to support a new path of exploration into compact, power producing reactors using the newly available high-temperature, high- superconducting technology.

Explore further: Explaining a mysterious barrier to fusion known as the 'density limit'

More information: Abstract: JT2.00001 Considerations of the high magnetic field tokamak path on the approach to fusion energy
Session Session JT2: Tutorial: Considerations of the High Magnetic Field Tokamak Path on the Approach to Fusion Energy

Related Stories

A new spin on understanding plasma confinement

November 10, 2011

To achieve nuclear fusion for practical energy production, scientists often use magnetic fields to confine plasma. This creates a magnetic (or more precisely "magneto-hydrodynamic") fluid in which plasma is tied to magnetic ...

Plasma experiment demonstrates admirable self-control

November 13, 2013

A team of Chinese and American scientists has learned how to maintain high fusion performance under steady conditions by exploiting a characteristic of the plasma itself: the plasma self-generates much of the electrical current ...

A promising concept on the path to fusion energy

March 31, 2014

( —Completion of a promising experimental facility at the U.S. Department of Energy's Princeton Plasma Laboratory (PPPL) could advance the development of fusion as a clean and abundant source of energy for generating ...

Recommended for you

Black butterfly wings offer a model for better solar cells

October 19, 2017

(—A team of researchers with California Institute of Technology and the Karlsruh Institute of Technology has improved the efficiency of thin film solar cells by mimicking the architecture of rose butterfly wings. ...

New type of electron lens for next-generation colliders

October 18, 2017

Sending bunches of protons speeding around a circular particle collider to meet at one specific point is no easy feat. Many different collider components work keep proton beams on course—and to keep them from becoming unruly.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Nov 24, 2015
Dilitium fusion is a clean source of power that will not produce radioactive waste. See our video on our INDIEGOGO crowdfunding at https://www.indie...584895#/
LENR can replace nuclear fission

Read more at:

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

Click here to reset your password.
Sign in to get notified via email when new comments are made.