The linked video and Kickstarter look more like a Farnsworth Hirsch inertial confinement reactor. Fusion reactions do occur in them, but a cold gas cloud forms at the center because of collisions with the physical electrode. What starts as a group of colliding and circulating beams quickly transforms into beam on target. The result is that ions only have a few chances to fuse before they lose too much energy.
My understanding of the Polywell is that it uses a trapped cloud of electrons to form the central cathode, which can help keep deuterium ions hot by reducing grid collisions.
The downfall I see is that you are still trying to "squeeze jelly with rubber bands".
The Brillouin limit describes the maximum steady state density possible in a non-neutral plasma.
In my device, the average density is well below this limit, but is briefly very very high. The goal is to have smooth and steady cyclotron trajectories most of the time, but all these trajectories intersect at the same point simultaneously.
https://www.kickstarter.com/projects/1992078142/building-the...