1. Quickstart

This quickstart describes how to use hypnotoad to create a grid for a single-null or double-null diverted tokamak configuration.

1.1. Installation

hypnotoad can be installed using pip:

$ pip install --user hypnotoad

or conda (from the conda-forge channel):

$ conda install hypnotoad

1.2. Usage

The magnetic equilibrium should be provided in the form of a geqdsk file (note the link requires a GA account to access), using COCOS-1 conventions.

The settings controlling grid generation are provided in a YAML input file. It is recommended to prepare this input file using the GUI, as described below. For reproducibility, produce the final grid file by running:

$ hypnotoad-geqdsk <path/to/geqdsk> <path/to/input.yml>

to ensure that the interactive nature of the GUI does not affect the grid file (it should not, but bugs are possible!).

To prepare input:

  1. Start the hypnotoad GUI:

    $ hypnotoad-gui

  2. Load a geqdsk file using the ‘Browse’ button beside the ‘geqdsk file’ box near the bottom of the window.

  3. (Optional) load settings from an existing input file, using the ‘Browse’ button beside the ‘Options file’ box near the bottom of the window.

  4. Adjust the settings in the table in the left side of the window. Help text for each setting is shown in a pop-up if you hover the cursor over the setting.

  5. Click ‘Run’ to create the set of grid points. Re-adjust the settings and repeat until you are satisfied.

  6. Save the settings using the ‘File’ menu, or the buttons near the top of the window (hover over the buttons to see descriptions). Note that ‘Save’ in the ‘File’ menu and the ‘Save options to file’ button will overwrite the existing input file (if one was loaded). Use ‘Save as’ or the ‘Save options to file with new filename’ button if you do not want to overwrite.

  7. You can click ‘Write Grid’ to create a grid file. This step will perform calculations of the geometric quantities required by BOUT++ and may expose problems with the grid generation, even when the process was successful up to this step. Note that as mentioned above it is recommended to create the final grid on the command line using a settings file for reproducibility.

Unfortunately, many problems can occur during grid generation. For some hints on how to solve or work around them, see Tips and tricks for fixing problems