New high-temperature superconducting materials are also compatible with high magnetic fields
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 magnetic field strength 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 plasma 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 "high-temperature superconductors" 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 fusion power, and even net electricity (Figure 1).
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-magnetic-field superconducting technology.
Contact: Earl Marmar, (617) 253-5455, firstname.lastname@example.org
Abstracts: 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
2:00 PM-3:00 PM, Tuesday, November 17, 2015
Room: Chatham Ballroom C
Saralyn Stewart | EurekAlert!
From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory
A two-atom quantum duet
12.11.2018 | Institute for Basic Science
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
13.11.2018 | Life Sciences
13.11.2018 | Life Sciences
13.11.2018 | Awards Funding