Question about Plasma Windows & Interaction with Magnetic Fields

[Halzman]

I've been doing some reading about both hot and cold plasma, when I had stumbled upon on article talking about a plasma window. [ http://en.wikipedia.org/wiki/Plasma_window ] The article goes on to mention a plasma valve.

Now, from what I understand - a gas is ionized (turned into plasma) and then that plasma is contained within a magnetic field.

My question's are in regard to how the plasma interacts with the magnetic field.

Does the gas have to be continiously 'pumped' in order to maintain the plasma window? - or - does only a small portion of a gas have to be ionized, and then the plasma itself is attracted to the magnetic field and 'bleeds' throughout the field, covering it to form a plasma window?

In either case, is the amount of gas ionized have an effect on the plasma windows strength/density? Or is it because of something entirely different?

I apologize if I posted in the wrong section.

 

[mfb]

Only some fraction of the atoms is ionized. The ions and electrons "resist" being moved orthogonal to magnetic field lines, providing the necessary force to keep the overall gas from expanding.