Quasineutrality

A plasma's tendency to keep equal ion and electron densities over any appreciable scale.

Beyond the tiny Debye length, a plasma maintains nearly equal positive and negative charge densities; any imbalance sets up strong restoring fields. Quasineutrality underlies the ambipolar physics that plugs the tandem mirror.

Beyond the tiny Debye length a plasma keeps its positive and negative charge densities nearly equal, because any imbalance sets up strong restoring fields. Quasineutrality is exactly the constraint that produces the ambipolar physics the tandem-mirror burner exploits to plug its ends.