Re: why does a "polywell" device contain electrons?

In article <1175021878.940290.201530@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Benj" <bjacoby@xxxxxxxxxxx> wrote:

Basically the device is a combination of a spherical magnetic field
and a magnetic mirror. The Lorentz forces you understand and describe
in essence cause the electrons to spiral around field lines. Therefore
if the field lines are more or less spherical the electrons attempting
to escape will be trapped circulating around the so-called spherical
magnetic "lines". In addition if the field is increasing as one
leaves the center there is a "magnetic mirror" effect (similar to that
found in the old [unstable] solenoidal confinement schemes).

Yes, in fact there is zero field at the center, and a quite strong one
near the outside, so I suppose the magnetic mirror effect is
substantial. (I still don't understand this effect in general -- how
can you reverse the velocity of an electron, without doing work on it?
-- but I'm trying.)

Of course, my question would be why electrons are not pouring
out through the "cusps".

Yes, that's a good question, one which the papers I've read have tried
to address, but much of the explanation is still over my head. It seems
to be a combination of: (1) these are only point cusps, not line cusps,
so the electrons can bounce around for a long time before they happen to
hit one -- like marbles in a wiffleball, thus the "wiffleball effect";
and (2) the field lines that exit the cusps circle around and plunge
right back into the center, in the later open-faced machines, so even
the electrons that exit the cusps are not always lost.

Indeed, what they call the "wiffleball factor" somehow describes the
likelihood of an electron hitting a cusp rather than bouncing magnetic
mirror-style. In a closed machine, the wiffleball factor determines
directly the lifetime of electrons in the machine, since any electron
that exits a cusp slams into the wall and is lost. In an open machine,
however, they say that this factor merely determines the density of
electrons inside the machine relative to electron density outside the
machine. This turns out to be a much more forgiving constraint (by a
factor of 1000), in terms of producing a useful potential well inside.

I would say more, but unfortunately the hard drive on my computer on
which is installed my patent-reading Tiff-file plug-in has crashed and
burned so I can only read the abstract of the patent at this time.

I have it in PDF form. Send me email (joe@xxxxxxxxxx) and I'd be happy
to send you a copy.

Best,
- Joe
.