Talk-Polywell.org

When current is passed through a coil of conducting wire that is insulated, the aggregate magnetic field is measurable and depends on things like - how many turns in the coil and how much current is passed. Obviously the resistance of the wire causes coil failure at high temperatures as the whole thing melts.

Copper is the winding of choice as it has the highest conductivity. (until we get a very long carbon nanotube that can be wound) Then, an iron core is used in the center to increase the field. ( by concentrating the field lines?)

Why dont we use a magnetic winding - like iron wire that has an enamel coating? This is conductive AND magnetic. (which should an even stronger field for a given current)

resistance

i clearly wasnt thinking straight.

if i did that, then maybe that's the opposite of using an iron core in an electromagnet. instead of packing the field lines more tightly around the core, you'd get a bigger 'hole in the middle'. The field lines would get concentrated around the windings. Dont know why i'd want that?! Also, the windings would get smushed together increasing the chance of failure. And of course, the increased resistance of iron...

sry, what a waste of bandwidth...if i had had thought it through, the solution would have been evident.

At least you are trying.

I'm not sure how the iron core (with copper windings) would effect the magnetic field outside the coil can. Certainly the iron core would displace space that might otherwise be used for windings or cooling. If this causes the magnetic field to be concentrated more towards the coil cans, this would possibly weaken the face point cusps. The edge/ corner/ line cusps probably wouldn't benefit either, as the opposing fields are already compressing the fields between the coils.
Would this iron core have some benefit in helping to magnetically shield standoffs or direct conversion grids? Again, I have no idea.

Dan Tibbets

The effect I see from an iron core in the cans is keeping more magnetic flux lines inside the can, something we don't want.