The plasmoid has angular momentum, which has to come from somewhere. Imagine a smoke ring spining around its axis. Since the velocity of the plasma in the plasmoid is a constant for a given ion, the larger the plasmoid, the more angular momentum per unit mass is needed. Injecting the angular momentum in theory should lead to a bigger plasmoid, up to the point that the plasmoid has all the energy in the device.
Also, without injected angualr momentum, the angualr momenutm is probably affected a lot by small variations in how the plasma runs down the electrodes. This may be a major cuase of the shto-to shot variability of the plasma focus. So injecting the momentum may make this variation much less.
By the way, this thread really belongs to plasma focus, not z-pinch.
