Talk-Polywell.org

Are there line cusps in the Polywell?

I have just re watched the Bussard Google talk where early on he briefly describes a mirror containment device consisting of two opposing ring magnets with a point cusp through the center of each ring and a line cusp extending radially from the equator between them. An equatorial line cusp if you will, or even better an equatorial plane cusp. If additional magnets are then placed opposing this equatorial cusp they would force any particles to divert around them. Would this effectively convert the line cusp into point cusps- through the centers of the additional magnets, or around the corners? Would point cusp physics then describe losses, or would line cusp physics still apply despite the distorted geometry? Using this analogy, I can see why having more faces would increase containment as the corner cusps would be more numerous, but have smaller total area (I guess).

Using the term 'plane equatorial cusp' allows me to better visualize the difference between the cusps, as the points are small holes through the center of the magnets while the equatorial line/plane cusp is thin but broad - fanning out from thw much wider outer magnetic field lines.

So, my layman's supposition is that the Polywell essentially converts the single axis/ 2 magnet mirror machine with two point cusps and one line cusp into a 3 axis (or more) machine with 6 magnets, 6 point cusps, 8 corner (point like or 'funny' ?) cusps, and no line cusps.

Is my reasoning correct? Does this 'modification' of the original line cusp make any difference? Are these the corner cusps that Bussard has referred to as funny cusps?

I think it's safe to say it is debated what happens. You might take a look at Possible wiffle-ball analytical solution, further in the thread there are some plots. It's the closest thing we have so far to seeing what happens to the line cusps. It appears to me that it forms into corner "funny cusps" and a middle point "very funny cusp". but...?

Wait until publication. I think you'll see a clear answer.

Thank you Tom. I was hoping publication would not be deferred due to DOD restrictions.

Regards,
Tony Barry

If you put the coils on the faces of a cube, the edges of the cube form the "line cusps". The center of each face and the corners are each "point cusps". The idea of "cusp" comes from fields joining - it is the place where peak field strength has to occur.

The idea of magnetic confinement is to have the particles circle around the field. Any particles heading straight out the edges, centers or corners will not feel a sideways force, and can directly escape. That's another reason it's called a cusp.

The collective properties of the plasma change how the particles behave in the cusps. What Bussard claimed, and what we have yet to learn about, is how the plasma and external fields interact to create long term confinement.