2D WB-7 B-filed simulation

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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MSimon
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Post by MSimon »

Why not model it as a series of concentric (to the presumed existing coils) coils each with reduced field?

Then your code might not have to change much at all. Just shrink the coils and reduce their fields.
Engineering is the art of making what you want from what you can get at a profit.

icarus
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Post by icarus »

kbaugh:

We modelled plasma as a diamagnetic (superconducting) sphere in this thread ... Indrek has Octave code available in the documentation somewhere there if you look
viewtopic.php?t=650&postdays=0&postorder=asc&start=0

Kelvin's method of images is a simple, effective place to start with the sphere.

kcdodd followed up with a "malleable" diamagnetic superconducting surface (approximating the outer electron sheath) that had plasma pressure equilibriating with the magnetic field strength "pressure" across it.

kbaugh
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Post by kbaugh »

As it turns out, I have the image coils implemented and running for the six-grid system, and should have the dodecahedron working by tonight sometime. I will post the files as soon as I can get the bandwidth. I will go back and look at kcdodd's results.

ladajo
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Post by ladajo »

The only really data point we have so far are limited photos of the test plasmas.

We know for sure that in the cube the plasma is not a sphere. It is spherical(ish), but with spikes (and maybe edges - but we have not seen a photo showing such yet). I agree the best comprehensive modeling we have seen so far was Indrek's and kcdodd.

Kbaugh: what happens in your model when you rotate the mirror coils to a 45 degree offset in the 3D?

kbaugh
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Post by kbaugh »

For what it's worth, here is an avi of the interior fields of a six-grid WB-7 class system which encloses a diamagnetic sphere whose diameter is 80% of the inscribed diameter of the grids:

Image

The background color again shows the log-magnitude of the total B-field strength (dB Re: Tesla). The diamagnetic sphere is modeled using Kelvins image method, but I have suppressed the fields interior to the diamagnetic sphere.

I was curious as to how the B-field established by the image coils compares to the B-fields produced by the true coils. Here is a plot of just the image coil fields for the six-grid system:

Image

In this plot, the background color shows the ratio of the image field strength to the (undisturbed) magrid field strength in decibels. I have again suppressed the field strength interior to the sphere, but due to a "feature" of MATLAB, I didn't suppress the streamlines in that region. The interesting thing to note is that the diamagnetic field is quite a bit weaker than the grid system field strength (by an order of magnitude or so). You can see some amount of "spikey-ness" in the image field.

Here is the same sort of plot of the total B-field (system and diamagnetic sphere) for the 12-grid system:

Image


... and here is the relative field strength of the image field to system field for the dodecahedron:

Image

The overall impression is that the 12-grid system is a bit more uniform (not too suprising), but I am not entirely satisfied with just "pretty pictures".

Can anyone suggest a quantitative figure-of-merit for containment in these kinds of systems? Does the "magnetic ratio" have any validity for these kinds of grids and systems? It would be relatively straightforward for me to evaluate B-field (and E-field) components along some set of B-field streamlines, but I'm not entirely sure what qauntitative measure would give the most insight into system behavior.

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