4193 revamp beam fusion calculations

[grmtrkngtn]

Description

Refactored beam_fusion model.

The model now directly computes beam alpha power from:

• fast beam ion density (from a slowing-down model)
• beam-weighted thermal target density
• beam-target fusion reactivity
• plasma volume

The previous thermal reactivity correction (Bosch-Hale) has been removed.

This was not physically consistent:

• thermal fusion involves two Maxwellian populations

• beam-target fusion involves one fast population and one thermal population

• the beam reactivity already includes fast-ion averaging

• See the docs for outline of the routine. I haven't changed much else of the physics but it's been listed more clearly in the docs in the new functional form.

• Most of the changes are clarifying what each function is actually calculating and changing docstring and name accordingly.

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.12%. Comparing base (25b9f07) to head (a6e43d8).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4200      +/-   ##
==========================================
+ Coverage   52.10%   52.12%   +0.01%     
==========================================
  Files         148      148              
  Lines       30389    30401      +12     
==========================================
+ Hits        15835    15847      +12     
  Misses      14554    14554              

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[je-cook]

Just comments on code and docstrings. I havent reviewed the model changes

[je-cook]

Codewise happy, leaving the model thoughts to @chris-ashe

[chris-ashe]

All of the mathematics in the docs is not rendering and the links are broken.

Just use

$$

<math_block>

$$

Will review the rest once I can see the equations

[grmtrkngtn]

All of the mathematics in the docs is not rendering and the links are broken.

Just use

$$

<math_block>

$$

Will review the rest once I can see the equations

It's rendering for me when I view the file on github. Could you show me what you're seeing?

[chris-ashe]

I think some CS changes from another branch have creeped in. I also cant get the summary file to plot. It just hangs.

[chris-ashe]

Just thinking if this is actually meant be the total field given by $\sqrt{B^2 + B^2}$?

[grmtrkngtn]

On the denominator? It's supposed to be $B^{2}$

$\beta = \frac{2 \mu_0 p}{B^2}$

Where B is the total magnetic field