♻️ Refactor CS coil by chris-ashe · Pull Request #4262 · ukaea/PROCESS

chris-ashe · 2026-05-19T14:51:08Z

This pull request makes significant improvements to the documentation and data structures for the central solenoid (CS) in the engineering models, as well as updates the plotting and cost calculation code to support new geometry and stress parameters. The main focus is on clarifying and expanding the CS geometry and stress calculations, adding new physical variables, and ensuring these are reflected throughout the codebase and documentation.

Documentation and Model Improvements:

Major expansion and clarification of the central solenoid (CS) geometry and stress calculation documentation, including new equations, definitions, and references.
Addition of new physical variables and parameters to the CS and PF coil data structures, such as inner/outer radii, toroidal area, steel area, cable space area, various stress profiles, and operating temperature.

Plotting and Visualization Enhancements:

Updates to CS coil structure and stress profile plots to include new parameters (e.g., toroidal area, hoop and radial stress profiles), and improved labeling and layout for clarity.

Cost Model Adjustments:

Cost calculations for PF coils now use the new a_cs_cable_space variable instead of the old awpoh, ensuring consistency with the revised data structure.

Documentation and Model Updates

Expanded and clarified the CS geometry and stress calculation documentation, including new sections on turn geometry, bore/peak field calculations, and explicit equations for radial and hoop stresses with referenced literature.
Added new variables to PFCoilData for inner/outer radius, upper/lower/middle z locations, toroidal area, steel area, cable space area, bore field, outer midplane field, and detailed stress profiles.
Clarified and renamed variables in BuildData for better consistency (e.g., specifying "radial" thickness).
Added temp_cs_superconductor_operating as a new input and data variable for CS operating temperature.

Plotting and Visualization

Updated CS coil structure plots to display the new toroidal area and improved axis/label formatting for stress plots.
Enhanced the main plot routine to include new subplots for radial and hoop stress profiles using the updated CSCoil and CsFatigue models.

Cost Model

Updated cost calculations for PF coil conductor and superconductor to use the new a_cs_cable_space variable, replacing the deprecated awpoh.

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 · 2026-05-20T08:09:01Z

Codecov Report

❌ Patch coverage is 68.61314% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.18%. Comparing base (6a55d75) to head (2923f21).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/models/pfcoil.py	67.56%	36 Missing ⚠️
process/core/io/plot/summary.py	22.22%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4262      +/-   ##
==========================================
+ Coverage   50.14%   50.18%   +0.04%     
==========================================
  Files         151      151              
  Lines       29355    29451      +96     
==========================================
+ Hits        14719    14780      +61     
- Misses      14636    14671      +35

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Copilot

Pull request overview

This PR refactors the Central Solenoid (CS) engineering model by introducing clearer CS geometry/turn-geometry data structures, expanding CS-related variables (geometry, stress, temperature), and updating outputs, plotting, and cost calculations to use the new fields.

Changes:

Refactors CS geometry and EU-DEMO turn geometry routines to return dataclasses and propagates new CS geometry variables through the PF/CS model.
Replaces legacy CS conductor+void area variable (awpoh) with a_cs_cable_space across models, costs, and tests; adds CS operating temperature input/variable.
Extends CS plotting and documentation to cover new geometry and stress quantities (including radial/hoop stress profiles and toroidal area).

Reviewed changes

Copilot reviewed 9 out of 11 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
tests/unit/models/test_pfcoil.py	Updates CS-related unit tests for new dataclass returns and updated CS stress/area APIs.
tests/unit/models/test_costs_1990.py	Updates cost-model tests to use `a_cs_cable_space` instead of `awpoh`.
process/models/pfcoil.py	Implements CS dataclasses, new CS stress/geometry fields, updated outputs, and adds CS stress plotting helpers.
process/models/costs/costs.py	Switches PF/CS cost calculations from `awpoh` to `a_cs_cable_space`.
process/data_structure/pfcoil_variables.py	Adds/renames CS data fields (geometry, areas, stress profiles, operating temperature).
process/data_structure/build_variables.py	Clarifies CS build-variable docstrings (radial thickness naming).
process/core/io/plot/summary.py	Updates summary plotting to include new CS stress subplots and CS toroidal area annotation.
process/core/input.py	Adds new input variable `temp_cs_superconductor_operating`.
documentation/source/eng-models/central-solenoid.md	Expands CS documentation with new geometry/stress sections and equations.

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@@ -10,6 +12,7 @@
 from process.core import constants
 from process.core import process_output as op
 from process.core.exceptions import ProcessValueError
+from process.core.io.mfile import MFile
 from process.core.model import DataStructure, Model


+        Parameters
+        ----------
+        r_stress_point : float/np.ndarray
+            Radial location at which to calculate the hoop stress (m)
+        r_cs_inner : float
+            Inner radius of the central solenoid (m)
+        r_cs_outer : float
+            Outer radius of the central solenoid (m)
+        j_cs : float
+            Current density in the central solenoid (A/m^2)
+        b_cs_inner : float
+            Magnetic field at the inner radius of the central solenoid (T)
+        f_poisson_cs_structure : float
+            Poisson's ratio of the central solenoid structure (dimensionless)
+
+        Returns
+        -------
+        float
+            radial stress at the specified radial location (MPa)
+


+    def calculate_cs_radial_stress(
+        self,
+        r_stress_point: float | np.ndarray,
+        r_cs_inner: float,
+        r_cs_outer: float,
+        j_cs: float,
+        b_cs_inner: float,
+        f_poisson_cs_structure: float,
+    ) -> float:


geograham

A few minor things and worth looking through the copilot suggestions.

geograham · 2026-05-28T13:42:09Z

The time labels on the currents profile over time plot are currently overlapping.

The red dot on the CS poloidal x-section plot is unlabelled.

geograham · 2026-05-28T14:07:33Z

-            - If the calculated conduit thickness is negative or too small, it is set to a minimum value of 1 mm.
+        - The calculation assumes a stadium-shaped cross-section for the CS turn.
+        - If the calculated conduit thickness is negative or too small, it is set
+            to a minimum value of 1 mm.


This was here when I got to the issue, I'm assuming this is to force it to a minimum viable value to prevent divide by zero errors.

geograham · 2026-05-28T14:19:01Z

 Switch `iohcl` controls whether a central solenoid is present. A value of 1 denotes that this coil 
 is present, and should be assigned a non-zero thickness `dr_cs`. A value of `iohcl` = 0 denotes 
 that no central solenoid is present, in which case the thickness `dr_cs` should be zero. No PF 
 coils should be located at positions defined by `i_pf_location(j)` = 1 if no central solenoid is present.


Could explain what i_pf_location(j) = 1 means.

This is outside the PR. I will actually write an enum for that asap

geograham · 2026-05-28T14:26:24Z

+
+The turn geometry is calculated as follows:
+
+1. The vertical height of the turn is given by:


I am getting some errors for the equations below, are they displaying ok for you?

You normally need to just refresh the page and they load

…rences

…ate documentation

…for improved accuracy

…erences

…oop stress calculation

…d update references

…n PF coil module

… module

…related variables

…e modules and update related references

…module

… module

…rameter types

…pdate plotting functions

…n methods

…plane

…itialization

…stency

… PFCoil model

…nd consistency

…ent divide by zero errors

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

…pport multiple return types

chris-ashe added CS Coil Refactor Variable rename labels May 19, 2026

chris-ashe force-pushed the refactor_cs branch 2 times, most recently from 11241c9 to 4c3139c Compare May 19, 2026 15:53

chris-ashe force-pushed the refactor_cs branch 3 times, most recently from 29f4622 to 035b649 Compare May 27, 2026 09:01

chris-ashe requested a review from geograham May 27, 2026 09:32

chris-ashe marked this pull request as ready for review May 27, 2026 09:32

chris-ashe requested a review from a team as a code owner May 27, 2026 09:32

Copilot AI review requested due to automatic review settings May 27, 2026 09:32

Copilot started reviewing on behalf of chris-ashe May 27, 2026 09:32 View session

Copilot AI reviewed May 27, 2026

View reviewed changes

timothy-nunn self-assigned this May 29, 2026

geograham requested changes Jun 1, 2026

View reviewed changes

chris-ashe force-pushed the refactor_cs branch from b6ced2e to 0a395e4 Compare June 1, 2026 14:04

chris-ashe added 12 commits June 3, 2026 09:56

Rename hoop_stress method to calculate_cs_hoop_stress and update refe…

ff19519

…rences

Enhance CS hoop stress calculation with additional parameters and upd…

733e1e1

…ate documentation

Refactor CS hoop stress calculation to include additional parameters …

54b5815

…for improved accuracy

Rename sig_hoop variable to stress_hoop_cs for clarity and update ref…

9eac826

…erences

Update CSCoil docstring to clarify parameters and add reference for h…

4a0925f

…oop stress calculation

Rename stress_hoop_cs variable to stress_hoop_cs_inner for clarity an…

35bd349

…d update references

Add stress_hoop_cs_inner_profile variable and update initialization i…

aa07620

…n PF coil module

Add a_cs_steel_poloidal variable and update initialization in PF coil…

d40452b

… module

Refactor CSCoil to calculate a_cs_steel_poloidal directly and update …

907a168

…related variables

Update output to reference a_cs_steel_poloidal in PF coil module

c47a5db

Refactor variable names from awpoh to a_cs_cable_space across multipl…

daaf07e

…e modules and update related references

Add inner and outer radius variables for central solenoid in PF coil …

db3e4b0

…module

chris-ashe and others added 23 commits June 3, 2026 09:56

Add radial inner and outer parameters for central solenoid in PF coil…

35e7a8b

… module

Add radial hoop stress profile plotting to CSCoil class and update pa…

abf7d8a

…rameter types

Refactor CSCoil class to add radial stress profile calculations and u…

e27cdbe

…pdate plotting functions

Refactor CSCoil class to rename and enhance magnetic field calculatio…

8664ca4

…n methods

Add peak field variable for central solenoid bore in PF coil module

fffd2e5

Add magnetic field variable for outer edge of central solenoid at mid…

13a63ce

…plane

Add operating temperature variable for central solenoid and update in…

15fb11d

…itialization

Update operating temperature for central solenoid superconductor

3cbe8bc

Post rebase fixes

e4a22cf

Update unit test

f20df1d

Add CSGeometry dataclass

f872c5a

Refactor CS stress plotting functions for clarity and consistency

fea7eb0

Update docs

897c564

❇️ Add a_cs_toroidal to store the top down cross section

9cdd435

Update CS geometry docs

cd97891

Add EU DEMO turn geometry calculations and update tests

fccf5fd

Refactor central solenoid variable descriptions for clarity and consi…

d2f5c1b

…stency

Refactor output comments and streamline superconductor information in…

18c0f0e

… PFCoil model

Refactor output formatting in PFCoil model for improved readability a…

0e242f8

…nd consistency

Update integration test MFILE data to include new CS outputs and prev…

b70e6c8

…ent divide by zero errors

Post rebase fixes

62402aa

Apply suggestions from code review

5cfac25

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Update type hint for central solenoid radial stress calculation to su…

058dab8

…pport multiple return types

chris-ashe force-pushed the refactor_cs branch from e93534e to 058dab8 Compare June 3, 2026 08:59

Post rebase fixes

050e98c


		The turn geometry is calculated as follows:

		1. The vertical height of the turn is given by:

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chris-ashe commented May 19, 2026 •

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