calibration.md

Calibration sources

legend-pygeom-l200 can easily be used to include the calibration sources deployed with the SIS.

As the position and types of sources frequently change, they are not hard-coded in the python code, but can be configured in a runtime configuration file.

TL;DR: a working example:

{
  "sis": {
    "1": {
      "sis_z": 8250,
      "sources": ["Th228", null, null, "Th228"]
    },
    "2": null,
    "3": null,
    "4": null
  }
}

calibration source configuration

The sis config object contains objects describing the deployed sources in each of the four SIS tube (or null, if no sources are deployed in that tube). The numbering equals the "official" SIS numbering scheme.

The sis_z coordinate is the SIS reading of the deployed SIS strings. The coordinate is transformed into simulation coordinates as described on the Confluence page.

Each SIS string has four slots for sources, that can be filled differently with this tool. The sources array contains the four slots from the top to the bottom. The bottom source is seated on top of the tantalum absorber.

Different types of sources can be included in the slots:

• Th228 — a normal LEGEND calibration source (as described in L. Baudis et al 2023 JINST 18 P02001).
• Ra — a special calibration source.
• ...+Cu — add a copper absorber cap to any other source. The dimensions of the cap can be seen in the code.
• null — no source in this slot. The tantalum absorber is placed irrespective of whether a source is placed inside in the slot.

Note

The generated geometry does not contain the requested source material. The decaying isotope has to be configured in the user's Geant4/remage macro file.

The volumes named source_inner_sis{SIS number}_source{slot} can be used as the confinement volumes in remage (i.e. with a regex ^source_inner_.*, if all sources share an isotope).