Triple product is necessary and partially sufficient. One of those products is "confinement time". Longer confinement times with lower density make for machin

Triple product is necessary and partially sufficient. One of those products is "confinement time". Longer confinement times with lower density make for machines that are closer to steady state rather than pulsed, greatly reducing engineering challenges. Stellarators are on the far end of the "steady state" spectrum while NIF is on the far end of the "high density" spectrum.