B field rect section v2

[t-atane]

I implemented the full B field for self-field in the winding pack according to the paper of Dr. Landreman
(https://iopscience.iop.org/article/10.1088/1741-4326/adb04e/meta).

Currently, the simsopt repository only includes B_regularized in src/simsopt/field/selffield.py (and also in the coil class in coil.py). I added B_0, B_kappa and B_b.

There are 3 main additions (the rest is due to autopep and ruff):
in selffield.py : the direct implementation of the different B field computation (from line 174)
in coil.py: the three B field contributions are added in the class "RectangularRegulaziedCoil" (from line 266)
in test_selffieldforces.py : added some assert to ensure that the tests pass for the new B fields (line 566 to 589)

This code has already been used by at IPP (Garching, Germany) for a paper about Ic-optimisation in the winding pack (currently in writing).

I remain available for any question.

Kind regards

[mbkumar]

@t-atane Can you please fix the linter errors?

[t-atane]

I mischanged the function coils_to_vtk in coil.py, which was not intentional. I thus restored the original function as it was. From all the unittests this was the only error I saw

[t-atane]

Are there other problems you were talking about @mbkumar ?

[codecov]

Codecov Report

❌ Patch coverage is 99.29577% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.47%. Comparing base (51b2245) to head (f4dd62e).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
src/simsopt/field/coil.py	98.70%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #640      +/-   ##
==========================================
+ Coverage   90.23%   90.47%   +0.24%     
==========================================
  Files          84       84              
  Lines       17899    17984      +85     
==========================================
+ Hits        16151    16271     +120     
+ Misses       1748     1713      -35     

Flag	Coverage Δ
unittests	90.47% <99.29%> (+0.24%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/simsopt/field/selffield.py	100.00% <100.00%> (ø)
src/simsopt/field/coil.py	97.78% <98.70%> (+0.21%)	⬆️

... and 3 files with indirect coverage changes

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[t-atane]

@mbkumar The pointed linting errors are not in the files I changed (I only changed src/simsopt/coil.py and selffield.py), so I am pretty confused. Do you want me to fix them anyway ?

[mbkumar]

@t-atane No need. I realized the errors thrown by the linter could be due to new rule enforcements by ruff. I'll investigate it.

[mishapadidar]

I may misunderstand, this can already be computed by building a BiotSavart object, not?