[Editors] MIT reactor aids study of potential energy source

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT reactor aids study of potential energy source
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For Immediate Release
TUESDAY, FEB. 13, 2007
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

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EDITORS: Gorgeous photos available
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CAMBRIDGE, Mass.--For about six months of the year, bursts of a hot, 
electrically charged gas, or plasma, swirl around a donut-shaped tube 
in a special MIT reactor, helping scientists learn more about a 
potential future energy source: nuclear fusion.

During downtimes when the reactor is offline, as it is right now, 
engineers make upgrades that will help them achieve their goal of 
making fusion a viable energy source--a long-standing mission that 
will likely continue for decades.

MIT's reactor, known as Alcator C-Mod, is one of several tokamak 
plasma discharge reactors in the world. Inside the reactor, magnetic 
fields control the superheated plasma (up to 50 million degrees 
Kelvin) as it flows around the tube.

Fusion occurs when two deuterons, or one deuteron and one 
triton--nuclei of heavy hydrogen--fuse, creating helium and releasing 
energy. The reactions can only occur at extremely high temperatures.

Although MIT's reactor is smaller than others, it has a stronger 
magnetic field than some larger reactors, allowing the plasma to 
become denser at comparable temperatures. "That positions us to 
provide important data you can't get anywhere else," said Earl 
Marmar, head of MIT's Alcator C-Mod project and senior research 
scientist in the Department of Physics.

One major goal of the upgrades is to create a system where plasma can 
flow in a steady state, rather than short pulses, or bursts.

Last year, engineers added a microwave generator that creates phased 
waves that flow around the ring, reinforcing the plasma current. The 
microwaves interact with the highest velocity electrons in the 
plasma, pushing them around the ring.

"It's possible to use this approach to go to fully steady-state 
plasma," Marmar said. "As an attractive energy source, ultimately we 
want steady state."

Benefits of a steady-state system include a constant energy output, 
less need for energy storage and less stress on the system, he said.

This year's modifications include the installation of a cryopump, 
which will allow scientists to control the density of the plasma over 
a long period of time--another necessary step to achieving a 
steady-state flow.

Several other modifications will allow the researchers to more 
accurately measure properties of the plasma, such as density and 
temperature. The new devices will also allow them to more accurately 
detect and measure magnetic and electric fields generated by the 
plasma.

The reactor, which has been offline for upgrades since August, is 
expected to be ready to use again starting in March.

More than 100 MIT researchers from the Departments of Physics, 
Nuclear Science and Engineering, and Electrical Engineering and 
Computer Science, including about 30 graduate students, use the 
Alcator C-Mod reactor to run experiments.

On a recent morning, the control room, normally packed with 
scientists at about 100 computer monitors, was nearly empty while 
engineers, scientists and students worked on modifications to the 
reactor, located in the next room.

When experiments are going on, researchers from around the world can 
participate in and watch the proceedings through the Internet.

There is high demand for time to run experiments on the reactor, but 
priority is given to projects that have high relevance to the Alcator 
goals and also to MIT graduate student research projects.

"One of our highest priorities is to get graduate students the run 
time they need," Marmar said.

For more information on the Alcator project, visit 
www.psfc.mit.edu/research/alcator/.

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