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Q & A: magnetic bottles

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Most recent answer: 10/22/2007
Q:
OK so i know that electromagnetic fields won’t bend visible light, but is there a way to use said fields to confine something else that is lightweight and "produceable" (like ions or electrons?) into a specific field of space and "collect" them or in some other way make them "dense"?
- Mark (age 22)
NC
A:
The question you ask happens to be crucial for the future of civilization. We need some large-scale long lasting source of usable energy. Nuclear fusion is perhaps the only such source we know of capable of sustaining a very large human population (like ours) for thousands of years. The main method by which people are attempting to achieve controlled nuclear fusion involves using magnetic bottles to trap a plasma containing the ions whose collisions create the fusion. These bottles certainly work for short times, etc. Whether they can be made to work for long enough times for hot enough plasmas to run useful fusion reactors remains to be seen.

Mike W.

On the more useless but still interesting end of the spectrum, non-static electromagnetic fields are used to trap neutral atoms in space. Sodium is one of the more popular ones because it has strong absorption/emission lines. By shining appropriately tuned laser beams (with frequencies just below the sodium line) in opposite directions in three dimensions, you can create a little trap for sodium atoms. This trap can cool the atoms down to fantastically low temperatures too. If a sodium atom is traveling towards one of the lasers, the laser light will be Doppler blueshifted closer to the absorption line and more scattering of the photons from that laser will occur, pushing the sodium atom back away from the laser. By doing this, you can slow down atoms so much they condense to form a Bose-Einstein condensate (there are more tricks needed to get the temperature low enough to do this).

See at nobelprize.org.

Tom

(published on 10/22/2007)

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