Hello DAVID!

03 May 05 10:03, DAVID WILLIAMS wrote to MICHIEL VAN DER VLIST:


 DW> As far as I know, fusion reactors have passed the point of
"physical" 
 DW> break-even, where the energy produced exceeds the energy required to 
 DW> fire the thing up, 

No, not quite... yet.
Apart from break-even there is another problem (well, of course there are
several, but this one is obvious): The most developed fusion devices
operate on the Tokamak principle. This involves (basically) a very large
transformer coil that induces a magnetic field to help confining and a
current to heat the plasma. Since a current is only induced by a changing
magnetic field (and thus a steadily increasing drive current) a Tokamak
reactor has neccessarily to be operated in pulsed mode. The length of the
pulses is the limiting factor for Asdex Upgrade right now, thus the plasma
burns for only ~5s. For a power plant you'll have to find a way to produce
electricity in a continuous manner. But you can probably solve this problem
by making the pulse duration longer and by building more than one device
operating in different phases (like the cylinders in a car's engine).
The other principle on which a fusion reactor can be built is the so-called
Stellarator. This would produce energy continuously by design, but it
requires a more sophisticated system of (supposedly super-conducting) coils
and rather complex magnetic fields. Thus research on stellarators is behind
research on tokamaks up to now, because tokamaks are easier to build.

People interested in research on fusion may like to visit the web pages of
the German experiments Asdex (Upgrade) (a Tokamak) and Wendelstein 7(X) (a
Stellarator) operated by the Max-Planck-Society, or JET (Joined European
Torus - the world's largest tokamak experiment up to now) and ITER (the
next-generation tokamak to be built hopefully soon):

http://www.ipp.mpg.de/ippcms/eng/pr/index.html>
http://www.jet.efda.org/>
http://www.iter.org/>


I must admit that I know only a very few things about recent fusion
experiments outside Europe (especially in the USA). NIF (National Ignition
Facility) that worked on laser-based fusion seems to have turned more or
less completely into a military experiment to simulate H-bombs or something
like that. Does anyone here know what US fusion researchers are up to these
days? Their politicians seem still to be busy trying to get ITER built
somewhere in the Nipponese mountains instead of lovely France...

 DW> but have not yet reached "fiscal" break-even, 
 DW> where the value of the energy produced, in terms of money, exceeds the cost 
 DW> of producing it. 
 DW> Money, of course, is a human fiction. 

Yep. And the "fiscal" break-even will depend heavily on the
development of the prices of energy produced in a different manner.


Regards,
Gerrit

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