Behind this unassuming door, off a small side street in
Cambridge Massachusetts, is the MIT Plasma Science and Fusion
Center. There's little indication that inside scientists are
using some of the most powerful magnetic fields in the world to
manipulate the same stuff that the Sun is made of. The first
stop was the Alcator C-Mod tokamak. A tokamak is a kind of
nuclear reactor that physicists hope will someday power cities
the of the future. Inside the big blue cylinder is a hollow,
doughnut shaped cavity where powerful magnetic fields start out
by compressing disperse plasma ions into a dense ring. The ring
heats up, and a nuclear reaction starts to take place when ions
get close to each other. Usually two ions repel because they
have the same charge, just like how two north pole magnets with
the same poles repel each other. But if they have enough energy,
the ions can overcome that repulsion and knock right into each
other. When that happens, the strong nuclear force takes over,
the two ions bond, releasing