Talk-Polywell.org

Billy,

I think that, as we now expect a much lower heat load, the use of multi layer materials for the first wall may not be necessary. It might now be possible to use Invar or a similar low thermal expansion material and thereby eliminate any remaining buckling problems due to thermal effects.

A mistake on my part there. Invar is ferromagnetic below the Curie temperature. It might just be appropriate if operated slightly above the Curie temperature (around 280C), but it will require experimentation to find what operating temperature will occur.

My first post here at Talk-Polywell. I got real excited about the technology and the possibility of practical fusion power production so I started reading and thinking about what you guys are trying to do. It seemed to me that the critical component is the design of the magnets, so I have been thinking about that. Some issues that seemed salient were coil weight, coil rigidity, temperature gradients, spacing between layers, coil cross section diameter, methods of attachments, and so on. Because I did not see it suggested I thought I would throw some things out for pondering by the resident brainiacs.

What about using a couple of layers of small diameter tubes for the water coolant. Water flow direction could be reversed for alternating tubes. Also, the water can be circulated to the back side of the torus to minimize temperature gradiants. Another reason for using tubes is that they add strength without a lot of weight.

Between the He layer and N2 layer, why not use an insulator instead of vacuum? It would seem difficult structurally to transfer loads across the space.

Struts supporting the coils could be made like wings so that electrons that strike them don't loose too much momentum (I am not sure if it is an issue, but if it is...).

Thanks for your indulgence, just throwing some wild thoughts out there.

Between the He layer and N2 layer, why not use an insulator instead of vacuum? It would seem difficult structurally to transfer loads across the space.

Because transfer of heat from LN2 to LHe is very expensive. (it is one reason thermos bottles were invented). It is going to cause engineering problems. What doesn't?

mvanwink5 wrote:....Struts supporting the coils could be made like wings so that electrons that strike them don't loose too much momentum (I am not sure if it is an issue, but if it is...).

Concering the wing (or wedge shaped -with the point facing the interior and the wires carried in the wide base) struts (nubs, interconnects), it wouldn't help because they carry the positive charge like the main magrid casings so the electron wouldn't ricochet off * but be immediatly absorbed and neutralized with resultant heating of the strut. But, what if the strut was insulated with a layer of very tough and smooth ceramic?. I'm pessimistic, but I suppose it might help some. Need to consider what happens to the electron after it bounces off. Will it have another chance to recirculate?. Will it (or ions) accumulate in the area and form a sheath that is harmful, or even benificial to the cusp behavior ? Interesting...

* At some kinetic energy an electron's behavior in such a collision might be more like a bullet than a charged particle, but I'm guessing that it would need to be much faster for that behavior to dominate.

Dan Tibbets

MSimon wrote:

Between the He layer and N2 layer, why not use an insulator instead of vacuum? It would seem difficult structurally to transfer loads across the space.

Because transfer of heat from LN2 to LHe is very expensive. (it is one reason thermos bottles were invented). It is going to cause engineering problems. What doesn't?

I suppose the supports have been worked out by existing sc manufacturers so just copy their designs. Thanks for the reply.

D Tibbets wrote:

mvanwink5 wrote:....Struts supporting the coils could be made like wings so that electrons that strike them don't loose too much momentum (I am not sure if it is an issue, but if it is...).

... But, what if the strut was insulated with a layer of very tough and smooth ceramic?. I'm pessimistic, but I suppose it might help some. Need to consider what happens to the electron after it bounces off. Will it have another chance to recirculate?. Will it (or ions) accumulate in the area and form a sheath that is harmful, or even benificial to the cusp behavior ? Interesting...

* At some kinetic energy an electron's behavior in such a collision might be more like a bullet than a charged particle, but I'm guessing that it would need to be much faster for that behavior to dominate.

Dan Tibbets

I guess I assumed the struts were coated by an insulation. Perhaps a static charge would also build up on the strut and reduce impacts from recirculating electrons.