From: Peter Hanely <hanelyp@nospam.calweb.com>
Newsgroups: sci.physics.plasma
Subject: Re: Effect of rapid rise time B field on dense plasma?
References: <a3m2sq$9v43$1@saturn.cs.uml.edu>
Organization: CalWeb Internet Services Inc. Your affordable ISP. (3)


Steve Ivy wrote:

>Assuming one has a moderately dense plasma
>contained in a moderate B field at some time.
>
>And then one subjects that plasma to a very strong,
>very fast rise-time, magnetic pulse say like
>what would be accomplished by a "can crusher"
>type single turn solonoid.
>
>Even without the flying mass of a "magnetized
>target" mechanism withs it's disposeable liner
>couldn't one get a substantial compression just
>using the B field acting on the plasma alone?
>
>Most of the experiments that I have read about
>that have attempted to create "magnetic bottles"
>have tried to do so with superconducting DC type
>coils. They were apparently trying to establish
>a static magnetic bottle that would then
>supposedly contain a plasma indefinitely.
>
>
>I won't waste time on that since apparently most
>everyone has given that up as a lost cuause.
>
I wouldn't call static confinement a lost cause. It's a given
that plasma will diffuse across a magnetic field.

>
>
>
>Instead I will elaborate on some ideas I have
>mentioned here earlier.
>
>
>I am suggesting that this whole magnetic bottle
>idea migh have gotten further if they had borrowed
>more from the pulsed power school of thought.
>
>I am not talking about the Z machine. That is a complex
>disposeable mechanism and making it work on a
>repetitive basis would be likely be tricky.
>
There's an old version of the Z pinch which uses a direct discharge
through gas, but I hear it's less effective.

>
>
>How about this instead.
>
>Take a "high pressure" gas. Where "high pressure"
>is undefined at this point but let's just say that
>it is a significant portion of room pressure (or most
>likely much higher).
>
>
>Now if you want to effect that gas with a magnetic
>field you will need it to be in a plasma state.
>
>
>So you hit it with a very intense (laser pulse
>,neutral beam or, microwave beam) So at least for a
>brief instant you have a very dense and at least
>moderately hot plasma.
>
Or electric discharge. High voltage low current should work well.

>
>
>Now you fire your main "can crusher" charge and you
>should get a very hot very dense plasma that will
>last at least a few microseconds.
>
>Basically I say the heck with all the fancy efforts
>at containment because a strongly riseing B field
>will act to collect the hottest ions right as you
>need them to be contained the most.
>
If the mean free path in the plasma was 'large', I'd expect charged
particles
to be swept up leaving many neutral particles behind. Your starting point
of 'high pressure at low temp' precludes this.

>
>
>On the other hand a static B field will become less
>effective at containment as the temperature of the
>plasma is raised by whatever means (neutral beams,
>microwaves or, laser pulse)
>
>As the ions push out harder due to higher temperature
>and gas pressure the magneti field will press that
>much harder inward. All this happening at just the
>right instant and no energy wasted maintaining or
>heating the plasma before it is needed.
>
>
>I suppose people have already tried this?
>
>If so can anyone suggest any experiments I can
>look up and see why this approach doesn't work well?
>
>
>I realise that counter currents generated by the plasma
>itself to oppose the rising external B field are likely
>to be a big issue but it seems to me that an extreme
>pulsed B field compression technique would be best able
>to deal with that sort of counter reaction.
>
>Also I don't see why one can't just create the needed
>plasma right at the last instant in a dense gas rather
>than wasting lots of energy trying to maintain it for
>long periods time in less dense gasses?
>
>
>Thanks for any pointers: Steve
>
While plasma (as any conductor) resists movement across a magnetic
field, it moves readily along a magnetic field. I'd therefor expect it to
quickly escape along the magnetic poles.

A quick fix for that might be a toriodal magnetic field.

Along that line, I recall seeing something about tokomaks with
compression heating.