Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility -- or "bottle" -- that will provide the next steps in the development of fusion reactors. Leading candidates include spherical tokamaks, compact machines that are shaped like cored apples, compared with the doughnut-like shape of conventional tokamaks. The spherical design produces high-pressure plasmas -- essential ingredients for fusion reactions -- with relatively low and cost-effective magnetic fields.
A possible next step is a device called a Fusion Nuclear Science Facility (FNSF) that could develop the materials and components for a fusion reactor. Such a device could precede a pilot plant that would demonstrate the ability to produce net energy.
Spherical tokamaks as excellent models
Spherical tokamaks could be excellent models for an FNSF, according to a paper published online in the journal Nuclear Fusion on August 16. The two most advanced spherical tokamaks in the world today are the recently completed National Spherical Torus Experiment-Upgrade (NSTX-U) at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), and the Mega Ampere Spherical Tokamak (MAST), which is being upgraded at the Culham Centre for Fusion Energy in the United Kingdom.
"We are opening up new options for future plants," said Jonathan Menard, program director for the NSTX-U and lead author of the paper, which discusses the fitness of both spherical tokamaks as possible models. Support for this work comes from the DOE Office of Science.
The 43-page paper considers the spherical design for a combined next-step bottle: an FNSF that could become a pilot plant and serve as a forerunner for a commercial fusion reactor. Such a facility could provide a pathway leading from ITER, the international tokamak under construction in France to demonstrate the feasibility of fusion power, to a commercial fusion power plant.
A key issue for this bottle 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. These differences, reflected in the shape of the magnetic field that confines the superhot plasma, have a profound effect on how the plasma behaves.
Designs for the Fusion Nuclear Science Facility
First up for a next-step device would be the FNSF. It would test the materials that must face and withstand the neutron bombardment that fusion reactions produce, while also generating a sufficient amount of its own fusion fuel. According to the paper, recent studies have for the first time identified integrated designs that would be up to the task.
These integrated capabilities include:
For pilot plant use, superconducting coils that operate at high temperature would replace the copper coils in the FNSF to reduce power loss. The plant would generate a small amount of net electricity in a facility that would be as compact as possible and could more easily scale to a commercial fusion power station.
High-temperature superconductors could have both positive and negative effects. While they would reduce power loss, they would require additional shielding to protect the magnets from heating and radiation damage. This would make the machine larger and less compact.
Recent advances in high-temperature superconductors could help overcome this problem. The advances enable higher magnetic fields, using much thinner magnets than are presently achievable, leading to reduction in the refrigeration power needed to cool the magnets. Such superconducting magnets open the possibility that all FNSF and associated pilot plants based on the spherical tokamak design could help minimize the mass and cost of the main confinement magnets.
For now, the increased power of the NSTX-U and the soon-to-be-completed MAST facility moves them closer to the capability of a commercial plant that will create safe, clean and virtually limitless energy. "NSTX-U and MAST-U 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.
Twice the power and five times the pulse length
The NSTX-U has twice the power and five times the pulse length of its predecessor and will explore how plasma confinement and sustainment are influenced by higher plasma pressure in the spherical geometry. The MAST upgrade will have comparable prowess and will explore a new, state-of-the art method for exhausting plasmas that are hotter than the core of the sun without damaging the machine.
"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 ability of these machines to create high plasma performance within their compact geometries demonstrates their fitness as possible models for next-step fusion facilities. The wide range of considerations, calculations and figures detailed in this study strongly support the concept of a combined FNSF and pilot plant based on the spherical design. The NSTX-U and MAST-U devices must now successfully prototype the necessary high-performance scenarios.
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 science.energy.gov.
John Greenwald | EurekAlert!
Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH
To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Life Sciences
28.04.2017 | Life Sciences
28.04.2017 | Life Sciences