Princeton Weekly Bulletin March 8, 1999
PPPL dedicates NSTX
"Spherical torus experiment" inaugurates new phase of fusion research
By Ken Howard
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Secretary of Energy Bill Richardson (c) at the
dedication with N.J. Congressmen Rodney Frelinghuysen
(R., 11th Dist.) (r) and Rush Holt (D,12th Dist.), and
children from P.J. Hill Elementary School in Trenton,
some of the approximately 2,000 school children and 200
teachers who participate each year in the Plasma Physics
Lab's K-12 science education program. |
Secretary of Energy Bill Richardson dedicated the new experimental fusion reactor, the National Spherical Torus Experiment (NSTX), and announced the production of "first plasma," a critical step in this fusion energy experiment. With Richardson were Rodney Frelinghuysen, a Republican member of Congress from New Jersey who has strongly supported fusion research as a senior member of the House subcommittee that provides funding for the U.S. Department of Energy, and Rush Holt, the newest Democratic member of Congress from New Jersey, who is a former assistant director of the Plasma Physics Lab. Also present were President Shapiro, the mayors of Plainsboro and Princeton townships, representatives from other fusion labs, and other dignitaries.
"This is an important moment," said Richardson. "We are marking the beginning of an operation that will bring us closer to the reality of fusion energy. The work being done in this lab has the potential to revolutionize the world."
NSTX is a prototype machine built for exploring methods to economically produce fusion energy, a form of energy created by joining two atoms in a thermonuclear reaction. Under design and then construction for almost five years, the new machine cost approximately $24 million to design and build. Current plans call for an initial five year phase of experimentation at an estimated budget of about $30 million per year. Sponsored by the Department of Energy and based at PPPL, NSTX was constructed in collaboration with Oak Ridge National Laboratory, Columbia University and the University of Washington. Approximately 13 research institutions will be involved in experimentation on NSTX.
"To those who question the utility of government funding for this kind of research, let me say that this remarkable project [the construction of NSTX] has been completed on budget and two months ahead of schedule," Richardson said.
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NSTX |
NSTX represents a next-generation fusion concept, a more compact and economical machine than its PPPL predecessor, the Tokamak Fusion Test Reactor (TFTR). "NSTX was designed and built on knowledge generated over the last decade, and particularly from experiments on TFTR," says NSTX project director Masayuki Ono. "TFTR demonstrated that fusion works, that it gives off power and functions as expected. We now need to demonstrate that fusion power can be generated more efficiently, so that it can become a practical energy source."
The search for alternative energy sources has ebbed and flowed with oil prices, and the current environment of relatively cheap and abundant fossil fuels has decreased government support for large-scale alternative-fuel projects and focused it instead on research for delivering simpler and less expensive systems, says PPPL Director Robert Goldston. "With present oil prices, a gallon of bottled water costs more than a gallon of gas," he points out. "Our focus right now is on innovation rather than building bigger machines. Our lab is exploring clever and innovative ideas to make fusion a practical and affordable power source."
Richardson underlined the importance of educating the American public to the need for fusion research and for improving its funding. "The work done in fusion has been important to our national security and to our national science goals," he said. "I believe this lab is important to the country, and I want to bring its funding back to a level worthy of a lab of national importance."
Goldston expressed the lab's appreciation to Richardson and to Congressmen Frelinghuysen and Holt, who along with N.J. Senators Frank Lautenberg and Robert Torricelli, are pressing for adequate funding for fusion.
The NSTX is part of PPPL's overall search for innovations for bringing fusion power "on line" as a national energy resource. The benefits of fusion energy include unlimited fuel (it comes from sea water) and clean production (no chemical combustion products contributing to global warming or acid rain), Goldston notes.
Other current pursuits of the lab contribute to NSTX while also representing their own separate lines of plasma and fusion research. This work includes on-site projects investigating plasmas for space propulsion and studying magnetic field behavior such as occurs at the surface of the sun. PPPL scientists also collaborate extensively on national and international fusion projects, working with over 100 different labs, universities and companies on fusion-oriented research.
Reaction that sustains the sun
Fusion energy has been around since early in the life of the universe; it is the reaction that sustains the sun and other stars. The challenge for scientists is to build a machine that produces and contains the reaction, and does it cost-effectively. The sun accomplishes this through the gravitational pull of its huge mass, keeping the fusion fuel contained in its core. A quart of fusion fuel on earth is equal in energy potential to about 6,600 tons of coal. In order for researchers to take advantage of this power potential, they must create the extreme conditions needed to sustain a fusion reaction while also containing the reaction.
Scientists have accomplished this in experiments lasting a few seconds. The most advanced experiments have used two forms of hydrogen as fuels: the isotopes deuterium and tritium. When these two elements come together and "fuse," a helium nucleus and a neutron are formed and large amounts of energy are released, using relatively little fuel. The reaction produces relatively low levels of radiation and no air pollutants, and cannot explode like Chernobyl nor sustain itself in a meltdown like Three Mile Island, Goldston says. The goal is to create sustained reactions to supply continuous energy.
In order to produce any fusion reaction, particles first need to be superheated to temperatures over 10,000 degrees Celsius. At this temperature, electrons are stripped from their nuclei, and a unique form of matter called plasma forms. This is actually the most common form of matter, making up over 99 percent of all visible matter in the universe, including all stars, says Ono. Closer to home, plasma can be seen in the flash of lightning and in the glow of fluorescent lights.
Once a plasma forms, its temperature must be brought to over 100 million degrees Celsius, six times as hot as the center of the sun, in order to coax the particles to overcome their nuclear repulsions and fuse. Along with the high temperature, there is also tremendous pressure and "turbulence," instability caused by the superheated plasma. The NSTX is designed to test new concepts in producing, containing and maintaining the plasma and reducing its turbulence.
Knowledge from TFTR
The design of NSTX builds on knowledge obtained from years of international fusion research with the tokamak, a doughnut-shaped machine that contains plasma in a "magnetic bottle," permitting control of the high-pressure high-temperature reaction. Originally conceived of in the 1960s in the Soviet Union, this design has since been under refinement at labs all over the world, including PPPL's TFTR project. In the spherical torus concept, the doughnut hole has been shrunk to the point where it almost disappears. The plasma is held in a nearly spherical configuration by powerful magnets and heated to fusion temperatures by an electrical current, by radio waves and by beams of energetic neutral hydrogen atoms.
"NSTX will test the key properties of the spherical torus," says Martin Peng, NSTX program director. "We will then be closer to a workable fusion furnace at a manageable size and cost. If we can successfully contain plasma with little turbulence then we have the ability to make a small sun on the planet Earth."
The NSTX project may yield important plasma discoveries with applications even beyond a practical energy source for the home. According to Peng, the information may include insight into applying neutron production to other areas of scientific research and discoveries to help build fusion rockets for deep space exploration.