A number of plasma physics papers I've seen mention "flux conservers", e.g. this paper. However, despite my best efforts, I can't find a good description of a flux conserver or how it actually works.
From what I gather, flux conservers are usually metal shells surrounding a plasma (let's assume a cylindrical shell for simplicity). Which flux is exactly being conserved? Is it the magnetic flux through the cross section of the metal shell? Or is it the magnetic flux that is actually inside the thin conductor? This latter idea makes sense to me since the magnetic field inside a perfect conductor shouldn't change. Is there an easy way to describe the effect of flux conservers on the fields inside the plasma? Can magnetic field sources external to flux conservers penetrate to the inside of a flux conserver? What is there usual purpose in plasma experiments?
Answers to any of these questions are much appreciated.