The B4 scaling is based on the B field strength facing the plasma center. Cusp losses is a somewhat different issue. It is related to the input current that is required to maintain the plasma pressure that may reach the limit determined by the B field strength facing the center. The cusps (central portions) do not change leakage with Wiffleball inflation, except the entrance into the cusp is pushed outward so that the vulnerable cusp surface area decreases while the total surface area increases. A funnel analogy has been described to illustrate this changing entrance geometry . As the Wiffleball inflates, the cone of the funnel is cut off till only the funnel tube itself (near parallel cusp B field lines ) remains. An hour glass may also be usefull. Mark the glass a certain distance from the center. Determine the collection area at that point on either side of the center. This represents the cusp collection area as the Beta= one condition is approached, then passed.KitemanSA wrote:True, but Dr. B seemed to think there would be a significant improvement, so who am I to argue? Could "excellent" be bettered?mvanwink5 wrote:KitemanSA,
Optimizing for leaking cusps might not be an issue requiring geometry efforts if confinement is excellent as reported by EMC2. Just a thought.
The B dependant density limits is, I think, related to the cross field transport losses as much as the cusp losses, at least under Wiffleball conditions where the cusp losses (with recirculation) may approach the cross field losses of electrons. Actually, in the patent application there is mention that excellent recirculation may allow for cusp losses to reach ~ 10X of the cross field losses. Theoretically, further cusp loss improvements could reach or become less than cross field losses. But,even if this is possible, thermalization issues may worsen, and even alpha particle cusp losses may become problematic (start heating the plasma). There is a sweat spot, or if you prefer, a Goldilocks situation.
Dan Tibbets