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PrincetonUniversity / SPEC

The Stepped-Pressure Equilibrium Code, an advanced MRxMHD equilibrium solver.
https://princetonuniversity.github.io/SPEC/
GNU General Public License v3.0
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is the iterfree testcase really iter? #19

Closed jloizu closed 7 years ago

jloizu commented 7 years ago

A Poincare plot of the iterfree.sp converged testcase does not show any X-point, the field-lines intersect the divertor in what I would consider "a non-realistic manner", and the computational boundary seems to be a flux-surface, see below:

iterfree_poincare_vessel.pdf

Is that supposed to be an actual iter equilbrium?

SRHudson commented 7 years ago

No, it is not supposed to be an iter equilibrium. Let's call it an iter-like. Spec does not know anything about the divertor. On the computational boundary (shown on your plot) the total normal field is set to be zero, so this is a flux surface. I have adjusted the vacuum component, Vns and Vnc, of the total normal field at the computational boundary to be exactly equal to the negative of the normal field, Bns and Bnc, produced by the plasma currents (computed by virtual casing). Generally, Vns and Vnc will be provided by the user. If you make small adjustments to these you can see how the position of the free-boundary plasma will change, and you can play around a produce an X-point in the vacuum region, which is the region outside the plasma boundary and inside the computational boundary.

jloizu commented 7 years ago

I understand, thanks!

Closing issue.