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Uniform energy spread could prevent tokamak disruptions
Uniform energy spread could prevent tokamak disruptions
Researchers at the 55th Annual Meeting of the American Physical Society (APS) Division of Plasma Physics this week have reported on efforts at the Alcator C-Mod and DIII-D experiments to investigate ways of dispersing the energy of disruptions.
Results suggest that the rotation of instabilities spreads the heat more evenly than the injection of gases like argon or neon. The rotation, which appears to be driven by smaller-scale instabilities, ends up moving the radiating regions around the vessel quickly and thus lowering the average heat load. Further research will determine if scientists can control or encourage this spontaneous rotation, and thus distribute the heat more uniformly to the wall.
Read the full article and access the APS abstracts at Science 2.2.
US Congresswoman Nancy Pelosi visited MIT's Plasma Science and Fusion Center (PSFC) and the Alcator C-Mod Tokamak, currently in "warm shutdown" status due to budget constraints.
Staff at the experiment are ready to restart operations should funding became available based on Congressional action on the fiscal year 2014 budgets.
Could fusion someday help power faster trips to Mars?
New propulsion technologies may blast astronauts through space at breakneck speeds in the coming decades, proponents say, making manned Mars missions much faster and safer.
Souped-up electric propulsion systems and rockets driven by nuclear fusion or fission could end up shortening travel times to the Red Planet dramatically, potentially opening up a new era in manned space exploration.
"Using existing rocket fuels, it's nearly impossible for humans to explore much beyond Earth," John Slough of the University of Washington, leader of a team developing a fusion-driven rocket, said in a statement earlier this year. "We are hoping to give us a much more powerful source of energy in space that could eventually lead to making interplanetary travel commonplace."
Fusion energy research is serious business. Generally, it is a lifelong commitment, involving long hours and weekends, along with optimism and dogged determination.
Recently, fusion research has been increasingly in the news, as construction moves forward on ITER in France, which is being designed and built by nations which together encompass most of the world's population. As an inexhaustible source of power, using seawater-derived fuel which is universally available, fusion energy is recognized as an urgent requirement for the future.
John Sheffield, who has been involved in fusion research for more than 50 years, has seen it all, including the foibles, missteps, failed experiments, and mistranslations that a global scientific research effort create. He has written "Fun in Fusion Research" to capture the very human and fun side of serious science.
Most scientific breakthroughs have occurred in boring buildings. Can a new generation of architects change that?
Today, expensive new physics buildings are being planned all around the world. The question is, are they any different from—or better than—their shabby predecessors? Should they express something of the wonder of the world they are built to examine? And will they help answers to the biggest questions emerge?
Like the Large Hadron Collider at CERN, the ITER Tokamak will be a monumental piece of machinery, a container capable of generating—and containing—a mini sun. ITER's Headquarters building, designed by Marseille-based architect Rudy Ricciotti and completed last year, features a dramatic undulating facade. There are many more buildings planned for the site, some more extravagant than others, but the box containing the Tokamak (the plasma-filled doughnut-shaped ball-of-fire container) is disappointingly utilitarian, looking like a big, boxy waste incinerator. Yet here, together with CERN, we have buildings searching for the holy grails of science—the Higgs boson, or "God particle", and the power of the sun. These really are our contemporary cathedrals, buildings embodying the power and strangeness of the subatomic world. Yet they express nothing of the wonder that the cathedrals tried to convey.
Read the full article on the website of the Financial Times Magazine.
Princeton astrophysicist Lyman Spitzer Jr. (1914-1997) was among the 20th century's most visionary scientists. His major influences range from founding the Princeton Plasma Physics Laboratory (PPPL) and its quest for fusion energy, to inspiring the development of the Hubble Space Telescope and its images of the far corners of the universe.
To honor Spitzer's achievements, some 60 scientists from around the world gathered at Princeton University 18-20 October for a 100th birthday celebration of the pioneering physicist. The event, sponsored by the Princeton Department of Astrophysical Sciences and hosted by Princeton astrophysicist and department chair David Spergel, ranged from personal reminiscences of Spitzer the man, to discussions of the latest developments in the fields of fusion, astrophysics and laboratory plasma science that he heavily influenced.
A magnetic filament of solar material erupted on the sun in late September, breaking the quiet conditions in a spectacular fashion. The 200,000 mile long filament ripped through the sun's atmosphere, the corona, leaving behind what looks like a canyon of fire. The glowing canyon traces the channel where magnetic fields held the filament aloft before the explosion. Visualizers at NASA's Goddard Space Flight Center in Greenbelt, Md. combined two days of satellite data to create a short movie of this gigantic event on the sun.
In reality, the sun is not made of fire, but of something called plasma: particles so hot that their electrons have boiled off, creating a charged gas that is interwoven with magnetic fields.
These images were captured on Sept. 29-30, 2013, by NASA's Solar Dynamics Observatory, or SDO, which constantly observes the sun in a variety of wavelengths.
Often the food analogies applied to tokamaks centre around doughnuts, due to the shape of magnetic field that confines the hot fusion plasma. But as one delves deeper into the complicated world of gyrokinetics, the simplistic doughnut transforms into a more complex banana orbit in a journey from the ideal to the real world.
The premise of the tokamak is to construct a doughnut shaped magnetic field and then the plasma particles will merrily spiral around it for ever. Enter an uncomfortable reality of geometry; as you can see in the main image above, the magnets are closer together in the centre of the torus (the hole of the doughnut) than they are around the outside. This means the magnetic field is not uniform: it is stronger in the inside part of the ring.
This means that the helical path the particle follows is not symmetrical. A tighter turn on the high field (inner) side of the line and looser on the outside leads to a drift either upwards or downwards (depending on the direction of rotation). This is the beginning of our banana orbit, as shown in the projected cross-section at the left-hand side of the figure. As an example, let's follow a particle on the inside of the banana halfway up, gradually creeping downwards to trace the banana's inner edge.