|
UW-Madison stellerator a step forward in plasma research
March 12, 2007MADISON-A project by University of Wisconsin-Madison researchers has come one step closer to making fusion energy possible.
The research team, headed by electrical and computer engineering Professor David Anderson and research assistant John Canik, recently proved that the Helically Symmetric eXperiment (HSX), an odd-looking magnetic plasma chamber called a stellarator, can overcome a major barrier in plasma research, in which stellarators lose too much energy to reach the high temperatures needed for fusion.
Published in a recent issue of Physical Review Letters, the new results show that the unique design of the HSX in fact loses less energy, meaning that fusion in this type of stellarator could be possible.
Plasma is very hot, ionized gas that can conduct electricity-essentially, it's what stars are made of. If heated to the point of ignition, hydrogen ions could fuse into helium, the same reaction that powers the sun. This fusion could be a clean, sustainable and limitless energy source.
Current plasma research builds on two types of magnetic plasma confinement devices, tokamaks and stellarators. The HSX aims to merge the best properties of both by giving a more stable stellarator the confinement of a more energetically efficient tokamak. "The slower energy comes out, the less power you have to put in, and the more economical the reactor is," says Canik.
Tokamaks, the current leader in the fusion race, are powered by plasma currents, which provide part of the magnetic field that confines the plasma. However, they are prone to "disruptions."
"The problem is you need very large plasma currents and it's not clear whether we'll be able to drive that large of a current in a reactor-sized machine, or control it. It may blow itself apart," says Canik.
Stellarators do not have currents, and therefore no disruptions, but they tend to lose energy at a high rate, known as transport. The external magnetic coils used to generate the plasma-confining field are partially responsible for the high transport rates in conventional stellarators. The coils add some ripple to the magnetic field, and the plasma can get trapped in the ripple and lost.
The HSX is the first stellarator to use a quasi-symmetric magnetic field. The reactor itself looks futuristic: Twisted magnetic coils wrap around the warped doughnut-shaped chamber, with instruments and sensors protruding at odd angles. But the semi-helical coils that give the HSX its unique shape also direct the strength of the magnetic field, confining the plasma in a way that helps it retain energy.
The team designed and built the HSX with the prediction that quasisymmetry would reduce transport. As the team's latest research shows, that's exactly what it does. "This is the first demonstration that quasisymmetry works, and you can actually measure the reduction in transport that you get," says Canik.
These results excited and relieved the researchers who have spent years working on the project. "We all thought the machine would do what it's turning out to do, but there are a million reasons why it might not: the theory might be wrong, (or) we might have built it badly," says Anderson. "But everything is panning out and supporting the fact that the ideas on which it was based were correct, and really points the way of the future for the stellarator."
The next step for the project is to establish how much symmetry in the coils is necessary to achieve low transport rates. They hope to make the coils easier to engineer, with the mindset that the principles used in the HSX could someday be incorporated into fusion generators, the reason that Anderson and his team began designing the HSX 17 years ago.
"It's an exciting field. It's something where one can contribute positively to mankind with an energy source that's completely sustainable, doesn't involve nuclear proliferation or radioactive waste, with a limitless fuel supply," says Anderson. "Plus, the machines look cool."
University of Wisconsin-Madison
Plasma is very hot, ionized gas that can conduct electricity-essentially, it's what stars are made of. If heated to the point of ignition, hydrogen ions could fuse into helium, the same reaction that powers the sun. This fusion could be a clean, sustainable and limitless energy source.
Current plasma research builds on two types of magnetic plasma confinement devices, tokamaks and stellarators. The HSX aims to merge the best properties of both by giving a more stable stellarator the confinement of a more energetically efficient tokamak. "The slower energy comes out, the less power you have to put in, and the more economical the reactor is," says Canik.
Tokamaks, the current leader in the fusion race, are powered by plasma currents, which provide part of the magnetic field that confines the plasma. However, they are prone to "disruptions."
"The problem is you need very large plasma currents and it's not clear whether we'll be able to drive that large of a current in a reactor-sized machine, or control it. It may blow itself apart," says Canik.
Stellarators do not have currents, and therefore no disruptions, but they tend to lose energy at a high rate, known as transport. The external magnetic coils used to generate the plasma-confining field are partially responsible for the high transport rates in conventional stellarators. The coils add some ripple to the magnetic field, and the plasma can get trapped in the ripple and lost.
The HSX is the first stellarator to use a quasi-symmetric magnetic field. The reactor itself looks futuristic: Twisted magnetic coils wrap around the warped doughnut-shaped chamber, with instruments and sensors protruding at odd angles. But the semi-helical coils that give the HSX its unique shape also direct the strength of the magnetic field, confining the plasma in a way that helps it retain energy.
The team designed and built the HSX with the prediction that quasisymmetry would reduce transport. As the team's latest research shows, that's exactly what it does. "This is the first demonstration that quasisymmetry works, and you can actually measure the reduction in transport that you get," says Canik.
These results excited and relieved the researchers who have spent years working on the project. "We all thought the machine would do what it's turning out to do, but there are a million reasons why it might not: the theory might be wrong, (or) we might have built it badly," says Anderson. "But everything is panning out and supporting the fact that the ideas on which it was based were correct, and really points the way of the future for the stellarator."
The next step for the project is to establish how much symmetry in the coils is necessary to achieve low transport rates. They hope to make the coils easier to engineer, with the mindset that the principles used in the HSX could someday be incorporated into fusion generators, the reason that Anderson and his team began designing the HSX 17 years ago.
"It's an exciting field. It's something where one can contribute positively to mankind with an energy source that's completely sustainable, doesn't involve nuclear proliferation or radioactive waste, with a limitless fuel supply," says Anderson. "Plus, the machines look cool."
University of Wisconsin-Madison
Plasma News and Current Plasma Events RSSPost-exercise caffeine helps muscles refuel
Recipe to recover more quickly from exercise: Finish workout, eat pasta, and wash down with five or six cups of strong coffee.
New paradigm for cell-specific gene delivery
Researchers from Northwestern University and Texas A & M University have discovered a new way to limit gene transfer and expression to specific tissues in animals.
Understanding the migration of cancer cells
Lamellipodia are veil-shaped protrusions of the plasma membrane, that can turn into upward-curled ruffles if they fail to adhere to the substrate.
Lavas from Hawaiian volcano contain fingerprint of planetary formation
Hikers visiting the Kilauea Iki crater in Hawaii today walk along a mostly flat surface of sparsely vegetated basalt. It looks like parking lot asphalt, but in November and December 1959, it emitted the orange glow of newly erupted lava.
Scientists find potential protein biomarkers for growth hormone
Ohio University scientists have identified several proteins in mice that might act as biomarkers for growth hormone. The research could be the first step to finding a more reliable way to detect recombinant human growth hormone (rhGH), which some athletes and teenagers use illegally to boost muscle and reduce fat.
Current screening test for prediabetes in children misses the diagnosis too often
Obese children, who are at increased risk for prediabetes and type 2 diabetes, may not be getting the most appropriate test to screen for these conditions, a new Canadian study found.
University of Florida professor designs plasma-propelled flying saucer
Flying saucers may soon be more fact than mere science fiction.
Scenes of nature trump technology in reducing low-level stress
Technology can send a man to the moon, help unlock the secrets of DNA and let people around the world easily communicate through the Internet. But can it substitute for nature?
Low HDL cholesterol from gene variation not associated with increased risk of ischemic heart disease
Lower levels of high-density lipoprotein (HDL) cholesterol due to a gene mutation is not associated with an increased risk of ischemic heart disease, according to a study in the June 4 issue of JAMA.
Smoking during pregnancy increases risk of SIDS
A new study provides the most direct evidence that there exists a causal link between smoking during pregnancy and Sudden Infant Death Syndrome (SIDS).
More Plasma News Articles
 | Welder's Handbook, RevisedHP1513: A Guide to Plasma Cutting, Oxyacetylene, ARC, MIG and TIG Welding by Richard Finch |
 | Statistical Mechanics: Entropy, Order Parameters and Complexity (Oxford Master Series in Physics) by James P. Sethna |
 | Introduction to Plasma Physics and Controlled Fusion by Francis F. Chen |
 | Introduction to Space Physics (Cambridge Atmospheric and Space Science Series) |
 | The Energy Machine of T. Henry Moray: Zero-Point Energy and Pulsed Plasma Physics by Moray B. King |
 | Statistical Mechanics by Kerson Huang |
 | Conversations on Electric and Magnetic Fields in the Cosmos (Princeton Series in Astrophysics) by Eugene N. Parker |
 | Plasma Chemistry by Alexander Fridman |
| Introduction to the Space Environment (Orbit, a Foundation Series) by Thomas F. Tascione | |
 | Plasma Physics and Fusion Energy by Jeffrey P. Freidberg |
| © 2008 BrightSurf.com |