Talk-Polywell.org

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.

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.

Taking output potential as 1.2MV that is only about 12A.

It appears that developments on the theory forum (Maximum size allowed...) mean that there may not be a significant first wall problem, which, from an engineering point of view, would be a great relief. Billy: You may find that your favoured structural shell becomes the first wall, as a high tempera...

I have a very tentative idea for the first wall mateial. A two layer material consisting of one of the Inconel alloys for the outer layer and pure copper for the inner layer. The outer layer to be in tension by bonding the layers with the Inconel at high temperature and the bonding process to be exp...

On the Design forum it has become apparent that the size of the cooling system for the Magrid coils will require that there be a large separation between the individual coils, at least an order of magnitude larger than the small number of gyro radii that are talked about currently. The close spacing...

There is a problem with lack of readily available high temperature data on some of the materials I have suggested for the first wall. It also appears that above the Curie temperature the thermal expansion coefficient ceases to be very low, and below this temperature the materials are ferromagnetic. ...

KitemanSA, I was referring to the casing of the high temperature water circuit which will have to function in the full heat of the sun. Billy has already identified thermal expansion as a problem because of the temperature difference between the front facing side of the toroid and the rear, which wi...

I think the real problem with Bitter s.c. magnets may be feeding in and switching the huge currents needed for start-up. The leads and temperature switch will be very bulky unless the plates are very thin, and thin plates would likely loose the advantages.

Elinvar is yet another possible first wall material of watchmaking origin.

Nivarox and Glucydur are non magnetic low thermal expansion alloys used in watchmaking. I have not yet found if they are weldable, but if they are they could be suitable for the first wall. What a change of scale!

Candidate alloy for high temperature water shell (first wall)? http://www.atlasbronze.com/C95800_properties.html Thermal expansion/permeability combination is the best I have been able to find. This is another possibility. http://cat.inist.fr/?aModele=afficheN&cpsidt=2647087 It's a pity Invar could ...

Billy,

Keep to the circular model until you have finished it. Complications are only for action later, and then only if they are really needed. We may discuss them, but what you are doing is the basic design which should be followed right through.

Modifying the core cross section might be the starting point for changing the outer profile. More field line calculations are needed.

Billy, I would like to congratulate you on having introduced some engineering realism to the Magrid design. As you say, you have a long way to go: keep up the good work. I have one suggestion, that you may not wish to incorporate at this stage, but which will need to be considered when you get a lit...