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.


I actually encountered the same problem. After some googling, here is my answer.

It is the magnetic field inside the conductor that is conserved. If a coil is short-circuited, then it must be flux conserving, for if there was a change in flux, a voltage would appear across the ends of the coil. Since the metal wall surrounding the plasma is perfectly conducting it is a flux conserver.

One example of application of this term is in spheromak research. Magnetic fields of a spheromak relax toward a nminimum energy state conserving the total magnetic helicity. A flux conserver is then the helicity barrier that sets the boundary of the minimum energy state. Changing the shape of flux conserver can affect the stability of spheromak equilibria.

reference: https://aip.scitation.org/doi/10.1063/1.874147


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