:orphan:

.. _AutoParamExampleAnchor:

Automatic parameter selection
=============================

This example contains the simulation of a plane wave (oblique incidence), scattered by a spiral of nine aluminum disks on a thin-film waveguide structure supported by a glass substrate 
Click :download:`here <../../../../examples/tutorials/07_automatic_parameter_selection/nine_disks_on_a_thin_film_system.py>` 
to download the Python script.

Test balloon simulation
-----------------------

The first part of the script runs a test balloon simulation, where the ensemble of nine disks is replaced by a single disk. An automatic parameter selection is triggered for the test balloon simulation. See the section on :ref:`AutoParamAnchor` for a description of the feature.

Actual simulation
-----------------

In the second part of the script, the resulting parameters (`l_max`, `m_max`, `neff_max`, `neff_resolution`) are copied to the actual simulation settings and the actual nine-particle simulation is run.

.. list-table::

    * - .. figure:: top_2D.png

           ambient DSCS

      - .. figure:: top_1D.png

           ambient DSCS (integrated over :math:`\alpha`)
					 
    * - .. figure:: bottom_2D.png

           substrate DSCS

      - .. figure:: bottom_1D.png

           substrate DSCS (integrated over :math:`\alpha`)

After the simulation has run, the differential scattering cross section is evaluated in a post processing step.
The left column shows the 2D-differential scattering cross section, :math:`\mathrm{DSCS}(\alpha, \beta) = \frac{\mathrm{dSCS}}{\mathrm{d}\Omega}`,
whereas the right column shows the 1D distribution (i.e., the integral over the azimuthal direction coordinate), :math:`\mathrm{DSCS}(\beta) = \frac{\mathrm{dSCS}}{\mathrm{d}\cos\beta}`.

In the substrate far field, the critical angle is visible as a ring-shaped feature.