Has there been any discussion on the arrangement of the cathode array? Is it possible that there would be an efficancy increase if they were arranged polygonally? A squatted hexagon comes to mind for me. If you view a torus “sideways” it appears similar to a flattened hexagon. Perhaps a rapid sequence following that shape, not around, but at polar opposites could increase pressures more rapidly. Per example 1 and/then 4, 2 and/then 5, etc. or other considerable permutations. It would be akin to nudging the instabilities along their path. This would of course require exquisite timing but may reduce the instentaneous stress on components that has been an issue.
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