Near Spherical Magrid

[rjaypeters]

Should we start a separate thread for Bussard ramscoop fusion chamber design?

[rjaypeters]

Tibbets four coil with Icarus split to standard dimensions:



Notes: 3m diameter, 0.2m coil assembly diameter and 6mm parallel coil spacing. Coil corner close approach >0.2m.

[rjaypeters]

Someone (Happyjack27?) asked for an analysis of Tibbets-Icarus with alternate coils removed:



I wasn't satisfied with the large gaps, so I removed the long coils onto the "prime" meridians and brought the corners close together (6mm) by using some fillets to preserve the 0.25m average corner radius* I'm using these days:



EDIT: * Actually, I using 0.26m in my models for the sketch before I project onto a sphere or other geometry. I'm using 0.26m to compensate for compound curvature once the projection lands on the the final geometry. I admit I'm too lazy to calculate the compound curvature.

[rjaypeters]

Along the way to producing the Tibbets-Icarus Alternate Coil Removed Meridianized I came upon this oddity:



I don't remember anyone describing an equatorial belt with polar caps.

[ltgbrown]

Some very interesting designs indeed!

Where do you see the supports attaching to your various structures?

[rjaypeters]

Short answer: I don't know.

Longer answer: The location of support structures depends on things I don't know, mostly the best locations to keep out of the way of the particles. I have the luxury to not worry about that detail.

OTOH, I will be happy to accept advice on where to put the structures (on the models!) based on reasonable physics and engineering arguments. AFAIK there aren't too many of those until we see some experimental results.

EDIT: The most recent diagram of an official WB I remembers shows the magrids cantilevered from the chamber walls. Nurbs, nubs connecting the coils at the closest approach is apparently a really bad idea. I can show other structure... but it's not my emphasis. I am thinking about how to get the current in/out/around and coolant in/out and that shows in some of the models.

[KitemanSA]

Tibbets four coil with Icarus split to standard dimensions:

If all the coils are the same polarity, I believe that would be Icarus' design. If the polarities alternate, this is just a real-real bowed octagonal with X-Cusps, my preferred design after the icosidodec and cuboct variants.

[KitemanSA]

EDIT: The most recent diagram of an official WB I remembers shows the magrids cantilevered from the chamber walls.

Oh? Where did this "official" design show up? There has been a lot of discussion about that very thing with no resolution to date. Maybe this will provide closure.

[rjaypeters]

KitemanSA,

This is the problem of having a really good visual memory, but not such a good one for internet locations. I thought I saw it on the EMC2 website, but a quick check shows nothing like I remember.

Sorry, I didn't mean to get any hopes up.

Anyway, care to weigh in on physical support concepts?

[rjaypeters]

...Where do you see the supports attaching to your various structures?

If cantilevers from the vacuum chamber wall aren't enough...maybe the "anti-nub" can help?


For the record, I hate this idea, but it may be less bad than a short nub.

[Ivy Matt]

This is the problem of having a really good visual memory, but not such a good one for internet locations. I thought I saw it on the EMC2 website, but a quick check shows nothing like I remember.

Were you thinking of this, perhaps?

[rjaypeters]

Yes, that's it, thank you.

So, the cantilever design isn't official. Ah, well...

[rjaypeters]

I think cantilever support from vacuum chambers will provide enough structural strength for magrids, but strength isn't everything. Perhaps damping* will be useful. The anti-nub can be skinny as long as we arrange the magnetic field around it appropriately.

This anti-nub has the same cross-section area as the previous picture.

*Pet peeve: dampening is not the same as damping. Take that science fiction authors!

[D Tibbets]

Such U-shaped interconnects have been proposed here before. The idea was that being further outside the magrid would allow a larger percentage of the electrons to recirculate before they reached that distance from the center. The perhaps strongest argument against this was an engineering concern, that such structures could not hold the magrid ridged against the repulsive magnetic forces. Taken to extremes, these U shaped nubs, when they stretch to the vacuum vessel wall, become standoffs. The advantages of this is that it keeps the 'interconnects' completely away from the center of the cusps till the Vacuum vessel wall and/ or other external structures (guns, collection grids, etc.) is reached. The forces from the magnetic fields would be in compression against the standoffs, which I understand is much easier to resist. Also, this allows each magnet to have it's own coolant supply. With high coolant flow requirements, this considerably eases things as a given flow only needs to cool one magnet instead of six (in a WB6 arrangement). The magnets effectively become isolated sub assemblies. This could have considerable advantages. If one fails, only it needs replacement, not the entire assembly. Also, complex curves are minimized. In an experimental setup where things are changing, this probably has advantages. A production machine may have a different set of priorities.

Dan Tibbets

[rjaypeters]

...The perhaps strongest argument against this was an engineering concern, that such structures could not hold the magrid ridged against the repulsive magnetic forces.

The open ring is about the worst structure one can have from a strength perspective. I think they might be useful damping vibrations induced from water, LN and LH flows through the rings (allegedly a lesser problem if we can use slower flows because alpha particles exit preferential through other cusps). We don't know the resonant frequencies of these structures imbedded in their magnetic fields. A prudent engineer includes damping, though not every coil close-approach may need an anti-nub to achieve sufficient damping.

Also, this allows each magnet to have it's own coolant supply.

Almost always useful for the reasons you give, and more.

But I still hate the interference with recirculation.