Question: How is the electron not getting into the machine?

[D Tibbets]

Just to nit pick,I do not think describing the magnetic fields as becoming concave towards the center when Beta >1 and this causing instability and loss of containment is acurate. Using the funnel analogy, or the multiple illistrations of the field lines in a Polywell, consider two funnels end to end with the narrow portion connected to each other. This narrow opening of the funnels do not change. The field lines here are parellel (or nearly so) to the center of the machine. What happens is that as Beta increases the magnetic field is pushed outward and this effectively flattens or chpps off the collecting cone of the funnel facing inward. When Beta=1 the surface of the Wiffleball has been pushed out to the point where all of the collecting cone has been eliminated. The narrowest portion of the funnel is unchanged (the cusp is not pinched) and the outer funnel morphology is unchanged. Once Beta>1 is reached the Wiffleball border has been pushed out past this midline where the funnels meet (the two cones of the cusp) and thus the opening is now increasing, Confinement drops in a reverse fashion. Not an instability, just a natural widening of the cusp hole as Beta increases further past one. This implies that with enough input electron current, the Wiffleball border could be pushed out further, but at increasing loss rates , and for that matter the B field may be pushed back into the cans elsewhere so confinement is blown anyway.

The point is that the magnetic fields facing the center (and within the radius of the Magrid mid plane) are always convex towards the center and thus always stable irregardless of the Beta. Of course as Beta >1 is reached the Wiffleball surface extending into the cusp region is at a greater radius than the Magrid so this analysis may be moot. Very close to Beta=1 in the real world miner fluctuations in the magnet current, local plasma variations, etc. may be enough to push these almost parallel field lines into local contortions that do result in instabilities. Beta=1 is an ideal limit. Practically Betas of ~ 0.95 to 0.99 might be the obtainable condition.

Dan Tibbets