Magnetic Fields and Plasmas
Can a magnetic field be used to contain plasma?
Yes it can. One of the projects on the table that has commercial
possibilities is called ITER - International Thermonuclear
Experimental Reactor - an attempt to harness fusion power to generate
electricity. In this configuration, the plasma is contained in a
toroidal (donut-shaped) magnetic field. The last news item I have on
this is from May 2005 in which Cadarache, France will be the site for
construction of this project, estimated to run around $5 billion. In
the US, Princeton has been a national leader in this research with
their National Spherical Torus Experiment. You could try googling
ITER, tokamak (the magnetic containment configuration) or FESAC -
Fusion Energy Sciences Advisory Committee, for more info.
Hope this helps.
Yes, but this has been compared to trying to hold Jell-o with rubber
bands. It can be done but you have to think about it.
The sun holds its plasma with gravity, but then the sun is pretty
big. A standard approach for fusion power is to hold a plasma in a
magnetic "bottle". People have imagined various ideas here over the
years. One that continues to be popular because it seems to work
better than some others is to put the plasma in a donut shaped
container, and hold it inside with strong magnetic fields. This
works because the plasma itself is electrically charged, and thus
wants to spiral around, or stay along, the magnetic field. If the
field closes back on itself, inside the donut, then the particles,
the plasma, stays too. But as I said, it is a sort of leaky bottle,
and this has been where much has gone.
This donut shaped bottle is called by a Russian word, Tokamak, since
the idea came from there. A large such machine is now being built
in France, it is called ITER (International Tokamak Experimental Reactor).
Just do a Google search on ITER Tokamak, or fusion power. When you
see things like "toroidal field coil", that is the magnetic --
toroidal meaning donut shaped, field for magnetic field, coil, well
it is made by wrapping a lot of wire, like a really big electromagnet.
YES! A magnetic field can be used to confine a plasma.
There are a few schemes to confine plasma, but among them the two best
to confine very hot plasma are magnetic and inertial confinement. There
is in fact a very fun physics problem regarding how it is possible to
confine a plasma with magnetic fields and impossible to confine a plasma
by purely using electric fields.
Sustained nuclear fusion requires a very hot, very dense plasma. Fusion
research scientists have invested a great deal of time and effort to
figure out the best way to confine a plasma. Currently there are two
giant projects underway, one of which uses magnetic confinement:
ITER, International Thermonuclear Experimental Reactor
When you are not concerned about energy loss or high temperatures is
possible to use simple glass walls as in the case of neon signs.
Michael S. Pierce
Materials Science Division
Argonne National Laboratory
Click here to return to the Physics Archives
Update: June 2012