Published by the MIT News Office at the Massachusetts Institute of Technology, Cambridge, Mass.
Published by the MIT News Office at the Massachusetts Institute of
Technology, Cambridge, Mass.
ALCATOR C-MOD Advenced Machine Produces Plasma The first major new tokamak fusion experiment to get underway in the United States since the early 1980s-the Alcator C-MOD-has begun operating at MIT's Plasma Fusion Center. Start-up plasma operations represent the culmination of more than four years of design, construction, and assembly, said Professor Ronald R. Parker, director of the MIT Plasma Fusion Center. The first plasma was achieved on October 21. The project, whose $18 million construction costs were funded by the US Department of Energy, will explore the behavior of the hot, dense plasmas required to create on earth the fusion energy that powers the sun and other stars. The plasma-a gas-like collection of charged particles-is confined in the Alcator C-MOD by a powerful magnetic field and heated initially by the electric current flowing through it. Additional heating in the form of radio waves will eventually be applied and is expected to raise the temperature to about 50 million degrees Kelvin. Professors Parker and Ian H. Hutchinson, head of the Alcator Division, expressed great pride in the job done by the project team led by David Gwinn. "The engineers, technicians and scientific staff have done a tremendous job in designing and building a beautiful machine. Now the physics team can begin to create and study plasmas at the very frontier of fusion research," Professor Parker said. The enormous magnetic forces within the Alcator C-MOD are sustained by a forged stainless-steel superstructure about two feet, thick (0.6 m) held together by high-strength alloy bolts four inches (100 mm) in diameter. The main magnets carry up to 250,000 Amps of current. The electrical energy they store can be delivered in about one second at a power (250 megajoules) comparable to the entire electric consumption of Cambridge. The energy level is provided by the Plasma Fusion Center's alternator, donated to MIT by General Electric on its retirement from utility service in 1976. The engineering challenges involved in the production and containment of the plasma are one major aspect in the pursuit of practical energy on a laboratory scale using fusion reactions, Professor Hutchinson said. Another is the understanding of plasma physics in magnetic fields. This involves wave and instability physics, turbulence, chaos, radiation, atomic physics, surface physics and many other fields. Alcator C-MOD is the third in a series of tokamak experiments at MIT, all of which have obtained excellent plasma confinement by the use of very high magnetic fields. Despite its name, which reflects its initial conception as a modification of Alcator C, Alcator C-MOD is essentially a completely new construction, Professor Hutchinson said. It is housed in the Nabisco Laboratory, NW21. (Nabisco, Inc., donated the building at 184-190 Albany St. to MIT in 1978.) Professor Hutchinson anticipates that the machine will be in the forefront of fusion research for most of the 1990s. "International fusion research stands at the threshold of scientific demonstration," he said. "Present large experiments in Europe, Japan and the US are operating near conditions of energy `breakeven' (fusion power out of the plasma equal to that needed to heat it). To make the step to the self-sustained burning plasmas necessary for a fusion power plant requires the construction of an experiment that is somewhat larger but, more important, one that incorporates advanced shaping of the magnetic confinement geometry and solves some of the difficult problems of particle and energy exhaust. "Alcator C-MOD is, in many respects, a scaled prototype of such a burning plasma experiment and will study many of the features and problems that will be encountered in the full-scale machine." The Alcator group is composed of approximately 100 people, including about 20 research scientists, and similar numbers of engineers and technicians. About 25 graduate students from the departments of Nuclear Engineering, Physics and Electrical Engineering and Computer Science are presently carrying out thesis research on the project.