Thanks Art. That just congealed a few ideas floating around from previous discussions. Let me check...Art Carlson (in Polywell In Europe Raising Funds) wrote:Both ions and electrons can be confined by a magnetic field everywhere parallel to the surface in a torus. In a sphere you have to have cusps somewhere. If you try to plug the cusps with electic fields, you have to decide whether to stop the ions or the electrons. You can't stop both.
1. As I now understand it, the magrid magnetic field contains the electrons, except at the cusps, where they jet out, but are recirculated due to the positive magrid. So no need to plug electrons at the cusp.
2. The quasineutrality of the electron jet out the cusps would drag ions with it, except (and I'm speculating here since I haven't seen mentioned) the positive charge on the magrid strips the ions from the electron jet. The neutrality at the cusps would be due to the combination of electron jet and positive charge on the magrid. To maintain neutrality the magrid charge would need to be finely balanaced against cusp jet size, although perhaps the cusp being overall positive rather neutral might be okay.
3. So in the Polywell at the cusp, the ions are being plugged by the positive charge on the magrid.
4. The subsequent (very speculative) image that forms is that all the ions trying to follow the electron jet out the cusp that are stripped gather around the cusp. Ion density grows at the cusp and its actually here that fusion occurs.
5. Actually I guess the ions stripped from the electron jet at the cusp now see the virtual negative electrode again and accelerate back towards the centre.