Exploring the Basics of Spheromak Configurations

[artis]

Hi, before posting I did a search both on google and here, there is not that much info out there.
The basic spheromak configuration that I could find resembles a tube with an inner electrode and and outer one (plasma gun) and a chamber at the end where the "plasma ring" expands into once it's created.

Is there also an axially oriented (field lines parallel to axial direction of tube) B along the length of the tube and the plasma ring "pushes" against it as it moves ahead?

Since there are inner and outer electrodes there must be a current running radially, also since gas is put in at the start of the plasma gun how is it ionized before the plasma ring forms?
in other words could someone please explain the basics of the B fields and currents in this plasma device machine.?

Artis.

 

[Astronuc]

Apparently, literature in the public domain is rather limited. I do see a number of papers available for purchase from IoP or Elsevier.

In the public domain.
https://str.llnl.gov/str/Hill.html

Diagrams may help one understand the evolution of magnetic fields.
https://web.archive.org/web/20110718062956/http://www.mfescience.org/sspx/pdfs/whatis-v2.pdf

https://www.osti.gov/servlets/purl/568022

http://www.cfn.ist.utl.pt/20IAEAConf/presentations/T6/1T/EX_9_5/Talk_EX_9_5.pdf

 

[Javier Lopez]

Apparently, literature in the public domain is rather limited

From now more limited after Researchgate had to remove millions of free papers from its site after lossing a lawsuit. A big loss for science.

 

[artis]

I see the common layouts of spheromaks, is the plasma created by pumping in the right gas mixture which passes the cylindrical electrodes and HV (AC or DC?) ionizes the gas creating a plasma which in the presence of B field is then pushed further into the expansion chamber where it can form into the donut shaped torus ring?

How does the ionization process happen? is the high voltage applied only briefly to ionize the gas and then low voltage high current is maintained like in a welder to sustain the arc and ionization?

 

[Javier Lopez]

Perhaps there is a breakdown so electrons passes between electrodes and heats the molecules to convert them to ions. I should use AC for that.
Also it can be used an antenna at 2.5GHz. Plasma is a very good conductor that takes RF fast
Another method is to use an electron source by heating a BaO surface at a negative voltage

 

[artis]

The PDF from J.B.Taylor and S.L. Newton that I'm reading states that the relaxed state in a spheromak is solely determined by the shape of the container? Now I only understand this partly because how is that so? Does the plasma torus own poloidal B field confines the plasma as the field interacts with the wall? Because if the plasma itself would interact with the wall strongly then it could not sustain itself?

 

[Astronuc]

The PDF from J.B.Taylor and S.L. Newton that I'm reading . . .

Is one referring to the text "Fundamental Concepts in Plasma Confinement"? It would help if one provided page number or section when citing the literature.

This may help to answer one's questions.
http://www-thphys.physics.ox.ac.uk/...aylor_paper1_relaxreconnectRevModPhys1986.pdf
See VI Relaxed States in Other Systems, A. Spheromak

 

[artis]

Yes I was referring to "Fundamental concepts in plasma confinement" PDF page 47.

 

[Astronuc]

Yes I was referring to "Fundamental concepts in plasma confinement" PDF page 47.

I believe one is referring to the statement, "Hence for a spheromak, the only relaxed state is the lowest eigenfunction: the eigenvalue determines μ and the field amplitude is determined by the sole invariant K. This means that, apart from a scale factor, the relaxed state in a spheromak is unique and entirely determined by the shape of the container."

Is one comfortable with the discussion about helicity and ∇ × (∇ × A) = μ∇ × A (Eq. 10.1 in the cited text)? How about Chapter 6, Plasma Relaxation?

 

[artis]

Well maths isn't my strong suit. Maybe firstly I would like to hear a more everyday explanation using fields etc if possible?
I was away for a while and will now proceed to reading the whole paragraph.