Re: Problems understanding irrational q values in Tokamaks

"Supertech" (is that you Charles?) wrote:

|> "Bruce Scott TOK" <[EMAIL PROTECTED]> wrote in
|> message news:[EMAIL PROTECTED]

[snip my discussion of tokamak magnetic field geometry]

|> Depending on how you simplify it.
|> 
|> Due to the gaussian velocity distribution of the plasma, there are always
|> some particles losing the grip of the magnetic field, drifting away from the
|> confinement.
|> 
|> Meaning that there is always a certain percentage of density leak in the
|> plasma.
|> 
|> Another way to put it is, confined hot plasma will never work.
|> 
|> I don't think it is so hard to understand.
|> 
|> That's why it never worked and it never will.

Well, statements like this are perfectly worthless if what they are
based upon is incorrect at an elementary level.

Your premise is ``Due to the gaussian velocity distribution of the
        plasma, there are always some particles losing the grip of the
        magnetic field, drifting away from the confinement''

And then you go on to say that this causes the ``density leak in the
plasma''

Unfortunately, that is an incorrect description of how particle
transport occurs in a magnetised plasma, so any statement you make based
upon it is, well, baseless.


In fact the fast particles on the tail of the distribution are as well
magnetically confined as any other.  The reason particle transport
occurs at the level it does is E-cross-B turbulence.  An elementary
(even trivial) result is that every charged particle has the same
E-cross-B drift velocity, since all that says is that the two pieces of
the Lorentz force cancel to good approximation.

The E-cross-B turbulence process is largely a fluid dynamics phenomenon
--- kinetic effects enter as corrections, and as dissipation
mechanisms.  That is why we can model the process with fluid equations.

For more on this subject at an elementary level which will prevent
readers from making the simple errors one often reads in this newsgroup,
see

    http://www.iter.org/
    http://www.pppl.gov/

-- 
cu,
Bruce

drift wave turbulence:  http://www.rzg.mpg.de/~bds/