[New example] "Anamak" tokamak toy examples

[kpentland]

Hi all,

I've added a new notebook into the examples that shows how to use the "Anamak" toy tokamak which I saw in the FGE arXiv paper. I've re-named this as Example07a and the SPARC example as Example07b. I've also removed the ITER example (Example08) - see note below.

The Anamak provides a nice testbed for solver testing. It enables you to build an arbitrary number of active coils, passive structures, and a limiter. You can then go on to create (almost) any plasma you want due to the arbitrarily large number of coils you can have. It could be a good way to compare against other equilibrium codes!

A few screenshots of some equilibria are below, let me know if there are any questions, comments, or typos!

Note on ITER example: One thing I did notice when playing around with the Anamak was when I tried to create a single null ITER/JET-like equilibrium. The inverse solver was converging but not registering that it converged. It then subsequently successfully carried out a forward solve (directly after the inverse) but returning a very badly shaped equilibrium (as other users have mentioned in past issues). I'll open another issue so that we investigate this properly.

Some equilibria from the notebook:

Circular machine, standard double-null, up/down symmetric, high positive triangularity:

Circular machine, standard double-null, up/down symmetric, high negative triangularity:

Elongated machine, standard double-null, up/down symmetric:

[georgeholt1]

@kpentland I haven't had chance to play with the anamak example just yet but will do so soon

Could you reinstate the ITER example though? It was fixed in #67

[kpentland]

Hi @georgeholt1,

All done - though I expect the notebooks test might fail because of some new plotting routines in FreeGS4E. Before merging this I think we'll need to check and merge #56.

[kpentland]

Merging in - if we need to make changes please open a new PR.