Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Spherical tokamaks could provide path to limitless fusion energy


Creating "a star in a jar" - replicating on Earth the way the sun and stars create energy through fusion - requires a "jar" that can contain superhot plasma and is low-cost enough to be built around the world. Such a device would provide humankind with near limitless energy, ending dependence on fossil fuels for generating electricity.

Physicists at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) say that a model for such a "jar," or fusion device, already exists in experimental form - the compact spherical tokamaks at PPPL and Culham, England. These tokamaks, or fusion reactors, could provide the design for possible next steps in fusion energy - a Fusion Nuclear Science Facility (FNSF) that would develop reactor components and also produce electricity as a pilot plant for a commercial fusion power station.

This image shows a test cell for National Spherical Torus Experiment-Upgrade with tokamak in the center.

Credit: Elle Starkman/PPPL Office of Communications

"New options for future plants"

The detailed proposal for such a "jar" is described in a paper published in August 2016 in the journal Nuclear Fusion. "We are opening up new options for future plants," said lead author Jonathan Menard, program director for the recently completed National Spherical Torus Experiment-Upgrade (NSTX-U) at PPPL. The $94-million upgrade of the NSTX, financed by the U.S. Department of Energy's Office of Science, began operating last year.

Spherical tokamaks are compact devices that are shaped like cored apples, compared with the bulkier doughnut-like shape of conventional tokamaks. The increased power of the upgraded PPPL machine and the soon-to-be completed MAST Upgrade device moves them closer to commercial fusion plants that will create safe, clean and virtually limitless energy without contributing greenhouse gases that warm the Earth and with no long-term radioactive waste.

The NSTX-U and MAST facilities "will push the physics frontier, expand our knowledge of high temperature plasmas, and, if successful, lay the scientific foundation for fusion development paths based on more compact designs," said PPPL Director Stewart Prager.

The devices face a number of physics challenges. For example, they must control the turbulence that arises when superhot plasma particles are subjected to powerful electromagnetic fields. They must also carefully control how the plasma particles interact with the surrounding walls to avoid possible disruptions that can halt fusion reactions if the plasma becomes too dense or impure. Researchers at PPPL, Culham, and elsewhere are looking at ways of solving these challenges for the next generation of fusion devices.

The fourth state of matter

The spherical design produces high-pressure plasmas - the superhot charged gas also known as the fourth state of matter that fuels fusion reactions - with relatively low and inexpensive magnetic fields. This unique capability points the way to a possible next generation of fusion experiments to complement ITER, the international tokamak that 35 nations including the United States are building in France to demonstrate the feasibility of fusion power. ITER is a doughnut-shaped tokamak that will be largest in the world when completed within the next decade.

"The main reason we research spherical tokamaks is to find a way to produce fusion at much less cost than conventional tokamaks require," said Ian Chapman, the newly appointed chief executive of the United Kingdom Atomic Energy Authority and leader of the UK's magnetic confinement fusion research programme at the Culham Science Centre.

The 43-page Nuclear Fusion paper describes how the spherical design can provide the next steps in fusion energy. A key issue is the size of the hole in the center of the tokamak that holds and shapes the plasma. In spherical tokamaks, this hole can be half the size of the hole in conventional tokamaks, enabling control of the plasma with relatively low magnetic fields.

The smaller hole could be compatible with a blanket system for the FNSF that would breed tritium, a rare isotope - or form - of hydrogen. Tritium will fuse with deuterium, another isotope of hydrogen, to produce fusion reactions in next-step tokamaks.

Superconducting magnets for pilot plants

For pilot plants, the authors call for superconducting magnets to replace the primary copper magnets in the FNSF. Superconducting magnets can be operated far more efficiently than copper magnets but require thicker shielding. However, recent advances in high-temperature superconductors could lead to much thinner superconducting magnets that would require less space and reduce considerably the size and cost of the machine.

Included in the paper is a description of a device called a "neutral beam injector" that will start and sustain plasma current without relying on a heating coil in the center of the tokamak. Such a coil is not suitable for continuous long-term operation. The neutral beam injector will pump fast-moving neutral atoms into the plasma and will help optimize the magnetic field that confines and controls the superhot gas.

Taken together, the paper describes concepts that strongly support a spherical facility to develop fusion components and create on Earth "a star in a jar"; the upgraded NSTX and MAST facilities will provide crucial data for determining the best path for ultimately generating electricity from fusion.


PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas -- ultra-hot, charged gases -- and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy's Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit

Media Contact

John Greenwald


John Greenwald | EurekAlert!

Further reports about: Nuclear PPPL Plasma fusion energy fusion power magnetic fields

More articles from Power and Electrical Engineering:

nachricht 'Super yeast' has the power to improve economics of biofuels
18.10.2016 | University of Wisconsin-Madison

nachricht Engineers reveal fabrication process for revolutionary transparent sensors
14.10.2016 | University of Wisconsin-Madison

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Innovative technique for shaping light could solve bandwidth crunch

20.10.2016 | Physics and Astronomy

Finding the lightest superdeformed triaxial atomic nucleus

20.10.2016 | Physics and Astronomy

NASA's MAVEN mission observes ups and downs of water escape from Mars

20.10.2016 | Physics and Astronomy

More VideoLinks >>>