From: Chris and Ken Doniger <c.k.doniger@worldnet.att.net>
Reply-To: k.doniger@ieee.org
Newsgroups: sci.physics.plasma
Subject: Re: New Hybrid MM ICF Approach.
References: <a1hjom$a6hm$1@saturn.cs.uml.edu>



Steve -
I used to be part of the magnetic confinement community.
It has been awhile, but I'll try to answer your questions.
My comments are in your text.

Steve Ivy wrote:
>
> Ok I have read enough about magnetic mirrors
> to know that one of their biggest problems is
> that they leak. But do they have to?
>
> OK so mind experiment time.
>
> Take a simple cylindrical solonoid.
> (eventually a superconducting one.)
>
> Now you generate a conventional DT plasma and
> try to contain it in your big solonid.
>
> Normally of course this would completely
> fail to contain the plasma.
>
> And here are the two primary reasons why.
>
> 1) There are two holes in the magnetic
> bottle. Big ones, right on the ends.
>
> 2) Due to the random nature of the motion of
> the particles in the plasma not every particle
> in the plasma will always have sufficient
> tangential velocity such that it will "see" the
> force of the magnetic field no matter how
> strong that field may be.
>
> It simple (F= qV X B) common sense. If there is
> No V in the Cross B direction then there is no
> force to constrain the particle to the center

No velocity in the cross B direction menas that the
particle isn't going to get out in the cross field
direction. Motion along a solenoidal field is
completely independent of the cross field motion.

> of the chamber. With no constraint normal gaseous
> diffusion will take place. Hot paticles begin to
> touch the wall, the plasma cools and, everything
> goes to heck.
>
> Well I have a (FIX) for both of those problems
>
> Fix # 1 (for the holes in the ends)
>
> Instead of jumping through endless hoops trying
> to cap the ends magnetically why not just plug
> them with a couple of powerful laser beams?

I don't know whether it is possible to make a laser
powerful enough to do this. Remember that lasers are
used to trap very cold atoms. A fusion plasma has
lots of kinetic energy.

In any event, you are pouring energy into the plasma
(via the laser) and slowing the particles. Your
(Power Out)/(Power In) ratio will head towards 0.
This is why B fields are so popular. They (sort of)
confine plasma without doing any work.

>
> Fix # 2 (What to do about diffusion)
>
> I suggest we provide a set of electodes within the
> solonoid. Picture a squirrlle cage assembly of non-
> ferrous electrodes. lining the inside of the solonoid.
>
> Now sequentially apply a high positive voltage to each of
> the electrode elements in turn. The electric field will
> be be made to rapidly rotate about the cage. So any
> positively charged particle that approaches the wall
> will attempt to avoid the moving electric field.
> But as the particle attempts to avoid that field
> it will now have a tangential velocity component and
> will thus be subject to the main magnetic field.

Fusion plasmas are good conductors, so electrics fields
don't often do what you might expect. Your squirrel-cage
design is reminiscent of a rotating B field concept that
was investigated in Australia. I don't know what became
of it.

I assume that your squirrel cage wires are not inside the
plasma, as that is a big no-no. The plasma always seems to
find a way to get to the wire and quench itself.

>
> This sort of arrangement will likely not entirely stop
> diffusion but it should slow it to a rate where it is
> no longer "a show stopper"
>
> One variation on this laser approach would be to apply
> a long medium intensity laser pulse to the plasm
> (to pack the plasma somewhat densely)
>
> Once the lasma is packed sufficiently dense one could
> hit the plasma with a brief but very intense main pulse to
> induce a propegating burn in the plasma.
>
> I would think that this approach is especially well
> suited as an adjunct to the new "Magnetized target
> fusion" program.
>
> Call it a Hybrid Magnetic Mirror Inertial Confinement Fusion
> or (HMMICF).
>
> let people from both of the biggest and oldest camps of
> fusion research work on it together. Peace at last.
>
> Thanks for any insight on where I have gone wrong.
>
> Steve Ivy