Skip to content

Importing Detector Geometry to ACTS

Step by step instructions for importing the Muon Collider detector geometry into ACTS.

Reference: ACTS Material Mapping Tutorial

The ACTSFun workspace contains helpful tools for creating a Muon Collider geometry that can be used by ACTS. The following instructions are based on a working setup of it.

Running the Geantino Scan

The geantino scan extracts the material (radiation lengths) from the detector geometry. There is an ACTS example program that can perform this scan on any DD4hep geometry. An explicit definition of the tracking volume is not required.

After editing response/geantinoscan.response to point to the DD4hep definition of your geometry, run the geantino scan:

${MYBUILD}/exts/acts/bin/ActsExampleMaterialRecordingDD4hep --response-file ${MYWORKSPACE}/response/geantinoscan.response

The output geantiono scan will be stored in geant4-material-tracks.root.

Converting DD4hep into TGeo

ACTS's DD4hep plugin requires the DD4hep detector tree to be structured in a specific way to correctly idenfity the logical components (ie: layers). The MCC DD4hep description does not follow this conversion. Thus the first step is to export the MCC DD4hep geometry into TGeo. ACTS's TGeo plugin is more "smart" about extracting the logical information.

General code for converting DD4hep to TGeo is available in the ACTSMCC package as the dd2tgeo tool.

${MYBUILD}/packages/ACTSMCC/dd2tgeo exts/detector-simulation/geometries/MuColl_v1/MuColl_v1.xml MuColl_v1.root

Validating Geometry

The MCC geometry can be validated by using the Fatras module to simulate hits in the tracking detector and visualize the results.

The tgeo-lctracker.response response file contains all the code necessary to load the TGeo MCC detector into ACTS. Make sure to edit it to update the path to your new TGeo ROOT file.

Run the following command to generate 1000 single muon events. The output will be stored in hits.root.

${MYBUILD}/exts/acts/bin/ActsExampleFatrasTGeo --response-file ${MYBUILD}/response/tgeo-lctracker.response --output-root --events 1000

The resulting hits file can be viewed using the study_geometry.py script.

python ${MYWORKSPACE}/python/study_geometryid.py

It should look something like the following. Volume ID Layer ID Layer ID, Barrel

Performing Material Map

This steps maps the geantino scan onto the volumes/surfaces of the tracking geometry.

  1. Convert the geometry into a JSON file (geometry-map.json).
${MYBUILD}/exts/acts/bin/ActsExampleGeometryTGeo -n1 -j1 --mat-output-file geometry-map  --response-file ${MYBUILD}/response/tgeo-lctracker.response  --output-json true --mat-output-allmaterial true --mat-output-sensitive false
  1. Convert the geometry JSON file into an easier to edit JSON file (config-map.json).
python3 ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/writeMapConfig.py geometry-map.json config-map.json

  1. Edit the config-map.json to choose which surfaces/volumes should have matterial mapped to them. This is done by changing the materialMap value to true.

  2. Convert the updated config-map.json back to geometry-map.json.

python3 ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/configureMap.py geometry-map.json config-map.json
  1. Calculate the material map. The result will be stored in material-maps.root.
${MYBUILD}/exts/acts/bin/ActsExampleMaterialMappingTGeo -j1 --input-root true --input-files geant4_material_tracks.root --mat-input-type file --mat-input-file geometry-map.json --output-root --output-json --output-cbor --mat-output-file material-maps --mat-mapping-surfaces true --mat-mapping-volumes true --mat-mapping-volume-stepsize 1 --response-file ${MYBUILD}/response/tgeo-lctracker.response

Validate Material Map

The validation step performs a geantino scan using the mapped material. The results are then compared against the scan done using Geant4. If the material map is correct, then the two should agree.

  1. Run the geantino scan of the mapped material.
${MYBUILD}/exts/acts/bin/ActsExampleMaterialValidationTGeo -n 1000 --mat-output-file val-mat-map --output-root true --prop-stepper 0 --response-file ${MYBUILD}/response/tgeo-mat-lctracker.response
  1. Make validation plots using ACTS' ROOT macros.
mkdir Validation

root -q -b ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/Mat_map.C'("propagation-material.root","material-maps_tracks.root","Validation")'

mkdir -p Surfaces/prop_plot
mkdir -p Surfaces/map_plot
mkdir -p Surfaces/ratio_plot
mkdir -p Surfaces/dist_plot
mkdir -p Surfaces/1D_plot

root -q -b ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/Mat_map_surface_plot_ratio.C'("propagation-material.root","material-maps_tracks.root","geometry-map.json",100000,"Surfaces/ratio_plot","Surfaces/prop_plot","Surfaces/map_plot")'
root -q -b ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/Mat_map_surface_plot_dist.C'("material-maps_tracks.root","geometry-map.json",-1,"Surfaces/dist_plot")'
root -q -b ${MYWORKSPACE}/exts/acts/Examples/Scripts/MaterialMaping/Mat_map_surface_plot_1D.C'("material-maps_tracks.root","geometry-map.json",100000,"Surfaces/1D_plot")'