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Configuration

FairShip builds its geometry from python/geometry_config.py, which reads a set of YAML files from $FAIRSHIP/geometry/ and takes a few options from the command line of run_simScript.py and run_fixedTarget.py.

Geometry YAML files

File Content
target_config.yaml Target layout (plates, materials, lengths). Default for both macros.
target_config_2026.yaml 2026 BDF target design (tungsten disks in a steel core). Select it explicitly.
veto_config_helium.yaml, veto_config_vacuums.yaml Decay vessel and veto layout. Chosen from the decay volume medium.
strawtubes_config.yaml Straw tube tracker (SST) layout.
MTC_config.yaml, SiliconTarget_config.yaml SND detectors (MTC and silicon target).

To try a different layout, copy the file, edit it and pass the copy on the command line instead of changing the default in place.

Command-line options

run_simScript.py:

  • --target-yaml <file> selects the target configuration, for example --target-yaml $FAIRSHIP/geometry/target_config_2026.yaml.
  • --helium (default) or --vacuums sets the decay volume medium and with it the veto YAML file.
  • --shieldName picks the muon shield from the database (TRY_2026 by default, or TRY_2025).
  • --SND turns on the SND; --SND_design chooses the design (1: emulsion target, 2: MTC and silicon target, or all).
  • --field_map files/<name>.root selects the spectrometer field map.
  • --strawDesign sets the tracker station frame material (10: steel, the default; 4: aluminium).
  • -g <geofile> reuses the geometry of an earlier run (on main, after 26.09). The geometry options above, apart from --field_map, cannot be combined with it (see Running).

run_fixedTarget.py has the equivalent --TARGET_YAML, --shieldName and --DecayVolumeMedium options, plus options for the beam position and spread (--x-offset, --y-offset, --z-offset, --beam-smear, --beam-paint).

Use --help on either macro for the full list and the defaults.