Something I have not read about in regard to the Bussard polywell is the ExB drift induced centrifugal forces around the maggrid. I have been reading about the use of centrifugal enhancement of simple mirror confinement, which operate in the 10kv range producing plasma rotations in over 100km/s. What is more interesting is the fact that because the electromagnetic forces on electrons and ions are equal, the centrifugal forces affect the ions much more because of their mass, which cause them to create a positive potential well at the center of the column.
In a polywell we are talking about voltages in the 100kv++ range. So I have started to ask myself what the implication of these huge drifts are in a BFR. They would push everything outward, toward the line cusps and away from the point cusps. They affect ions more then electrons, so you may get some extra charge imbalances. There may be extra currents since we are dealing with a non-neutral plasma, in addition to the direct force on the magnetic field due to the centrifugal forces. Mainly I just want to bring the topic up to hear what other people think.
Centrifugal Forces
Centrifugal Forces
Carter