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Name: Kurt
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Question:
Can a magnetic field be used to contain plasma?



Replies:
Hi Kurt 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.

Bob Froehlich


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.

Steve Ross


Hello Kurt,

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
http://www.iter.org/a/index_nav_4.htm

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



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