Talk-Polywell.org

I've decided I want to build a version based on the WB1 design, using permanent magnets.

I have a 22cm diameter glass bell jar available, what size does this restrict me to WB design wise ?

I am very much a beginner when it comes to these things, so I have heaps to learn.

(If anyone wishes to donate to help towards this, feel free!)

http://fusor.net/

These guys build them all the time.

I came from there to here

I want to try the non-fusor approach. (I was going for the fusor approach, now this WB+ approach looks more me.)

Nanos,

I just accidentally scrolled down this far and found your post.

From memory, I'd say WB-1 was made of donut magnets about 1/3 to 1/4 the diameter of the vacuum chamber it was in. You could probably find small ceramic donuts that fit your chamber.

I've got a set of 6 that are about the size for a WB-3, but I never did anything with them. They would need about a 3-foot diameter chamber.

I've been wanting to see somebody build one of these. It won't do fusion, but it will make a neat glow discharge. I don't think WB1 was ever run at more than a few hundred volts.

My impression is that WB-1 used magnets where the poles were opposite flat faces. A variant of WB-1 that might be interesting is if you could get, or make, ring magnets where one pole is the outer face, the other pole the inner face. Space the magnets apart a little like WB-6. I don't expect better than WB-4 electron containment, but the magnetic field lines running parallel to the faces facing the plasma may be interesting.

hanelyp,

There are photographs of WB1 knocking about. Figure 5 of the Askmar version of my recent Analog article shows it.

http://www.askmar.com/Fusion_files/2008 ... isited.pdf

The ring burned into the flat faces is where the field lines enter, and are the serious loss path. On this model, one flat face is N and the other S, with the same pole pointed in on each magnet.

If I understand what you are trying to suggest, you would want a magnet magnetized radially. For example, the N pole might be on the outer edge and the S pole might be to the inside diameter. Thus, the face adjacent to the plasma would have field lines paralleling this face. That would not stop the loss, but it ought to be a significant improvement.

I have no idea how you would obtain magnets to that spec. Anybody?

Tom Ligon wrote:If I understand what you are trying to suggest, you would want a magnet magnetized radially.

Exactly.

Tom Ligon wrote:I have no idea how you would obtain magnets to that spec. Anybody?

I have 2 ideas:
- Piece together rings from bars with beveled ends.
- Re-magnetize a ring with the orientation you want by sandwiching it between a pair of pancake electromagnets. A brief high intensity pulse should do the job. This would be a decent project in itself.

Ceramic magnets will resist being remagnetized like that. I'd have to look up their manufacturing process. It could be that you have to heat them above their Curie point, apply the desired field, then cool them with the field applied.

Ceramics were chosen for that job because:

1. Their Curie point is relatively high so they would stay magnetized when exposed to the heat from the electron gun

2. Rare Earth magnets would be stronger but are hard to find in that form factor, and demagnetize at a much lower temperature.

3. His favorite surplus house had them in stock.

I've considered rare earth magnets plus a cooling jacket. You can't weld the jacket on because the welder will quit on you when he tries to control an arc in that field. Good epoxy might work.

Master Bond makes some good high vacuum epoxies. They don't sell them that way though. You have to ask for low outgassing/space rated stuff.

Someone mentioned to me about ceramics and dentistry might provide suitable materials.

I was wondering about a ceramic overcoat made in two halves with the magnets inside.

Would a halbach array approach offer any benefit here ?

(Says he making wild stabbing in the dark motions from his lack of understanding at the issue.)

Honestly, WB1 was made by wiring what amounted to a pair of stainless steel washers on the faces of the magnets. The inner washers had tubes going thru the holes of the magnets. These could be welded in place prior to installation on the magnets.

Fitted cases are preferable, but the main concerns are to make it physically sturdy and to make the surfaces conductive.

Low outgassing Epoxies:

http://www.masterbond.com/overview.html#oaero

pdf:

http://www.masterbond.com/sg/masterbond_losg.pdf