single_stage_optimization

Optimization of stellarator devices using a single stage approach

Requisites

• SIMSOPT: install branch single_stage from https://github.com/hiddenSymmetries/simsopt
• VMEC2000: https://github.com/hiddenSymmetries/VMEC2000
• booz_xform: https://github.com/hiddenSymmetries/booz_xform
• (for finite beta cases) virtual-casing: https://github.com/hiddenSymmetries/virtual-casing

Other python requisites available in requirements.txt

Note: aditional plotting routines available if python library mayavi is installed

Run the code

Launch directly the main.py file using

./main.py

or launch it using python (or python3)

python3 main.py

Input parameters

The input parameters are sent via the command line.

• Quasisymmetry flavour: choose ./main.py QA, QH or QI to choose the vmec input file and objective function. If the two letters are not present, defaults to QA
• Stage: add --stage1, --stage2 or --single_stage when running main.py to select which optimization stage to use
• All other inputs can be seen in file src/inputs.py. Their default values can be changed in the input terminal. For examples, to change the number of iterations of the single stage optimization to 20, one just needs to write --MAXITER_single_stage 10 in the terminal.

Simulation results

The output of the code is stored in a folder called results which contains, among other things, the coils and the boundary surface, which can be visualized using the Paraview software.

To see live the results of the optimization check the file output.txt with, for example, tail -f output.txt.

Examples

• ./main.py QI --stage_1 runs only stage 1 for quasi-isodynamic symmetry with the default parameters that are in the file src/inputs.py at that time.

• ./main.py QA --single_stage does the same but for quasi-axisymmetry and for a single-stage optimization.

• ./main.py QI --single_stage --ncoils 10 --max_modes 4 ----MAXITER_stage_2 1000 runs single-stage with quasi-isodynamic symmetry, 10 coils per half field period, changes to 4 the number of Fourier mode resolution for the plasma surface and to 1000 the number of iterations of stage 2 performed in the beginning. This last parameter may seem mute for single-stage optimization but is in fact crucial due to the initial stage 2 that is performed in order to obtain the starting coils.

Plots

• After running the code, it is possible to obtain certain plots of the results which are not immediately created. They require the installation of VMEC2000 and booz_xform (# Requisites).

• These are created and obtained by running plot.py file.