Experimental geometry¶

remage does not implement or manage any experimental geometry. Instead, the user must provide a geometry definition. There are two supported approaches:

Supply one or more GDML files via the command line or using the macro command /RMG/Geometry/IncludeGDMLFile.
Override RMGHardware::DefineGeometry() in a subclass of RMGHardware and register it using RMGManager::SetUserInit(). A practical example is in examples/02-hpge.

Registering sensitive detectors¶

Sensitive detector volumes must be registered so that particle interactions are recorded in the output. In remage, this can be done in several ways. Each detector has a unique id (UID) and a type, which determines how hits in a physical volume (or in a group of them) are processed and stored. Detector of type Germanium, Scintillator and Optical are currently supported, see Output for more details.

Note

User-defined detector types cannot currently be registered at runtime.

The simplest method is to use the /RMG/Geometry/RegisterDetector macro command:

/RMG/Geometry/RegisterDetector Germanium B00000B 1
/RMG/Geometry/RegisterDetector Germanium C000RG1 2 1

This registers the physical volume B00000B, and the C000RG1 volume with copy number 1 as Germanium detectors with UIDs 1 and 2 respectively. Because for B00000B no copy number was specified, this will register all B00000B named volumes if there are multiple with different copy numbers. This command now also accepts regex patterns (respecting the default std::regex_match grammar):

/RMG/Geometry/RegisterDetector Germanium B.* 1

registers all physical volumes starting with B. If there are multiple volumes matching the pattern, they will all be registered alphabetically under incrementing UIDs. This means the first alphabetical B.* match will be registered under UID 1, the second match will be registered with UID 2 and so on. It is therefore the responsibility of the user to make sure that no UID will be duplicated, which is detected by remage and results in an error.

Alternatively, one might want to assign the same UID to multiple physical volumes, i.e. as if they constitute a single detector unit. In such a scenario, there would be no way to distinguish hits from different volumes in the simulation output (except from the coordinates in post-processing). In this case, the fifth argument (allow_uid_reuse) has to be set to true:

/RMG/Geometry/RegisterDetector Germanium .*_cu_.* 1 .* true

This would register any volume with name matching the regular expression .*_cu_.* under the UID 1. In this case the UIDs will not be incremented for multiple matches.

Last but not least, detectors can be imported from a GDML file that includes metadata, using the /RMG/Geometry/RegisterDetectorsFromGDML command.

Tip

The legend-pygeom-tools package automatically includes such metadata when writing GDML with pygeomtools.write.write_pygeom().

Inspecting geometry¶

To inspect the simulation geometry, use the following macro commands:

Example session:

remage> /RMG/Geometry/IncludeGDMLFile geometry.gdml
remage> /run/initialize
G4GDML: Reading 'geometry.gdml'...
G4GDML: Reading definitions...
G4GDML: Reading materials...
G4GDML: Reading solids...
G4GDML: Reading structure...
G4GDML: Reading userinfo...
G4GDML: Reading setup...
G4GDML: Reading 'geometry.gdml' done!
Stripping off GDML names of materials, solids and volumes ...
[Summary -> Checking for overlaps in GDML geometry...
remage> /RMG/Geometry/PrintListOfPhysicalVolumes
[Summary ->  · B00000A  // 0 daugh. // 5.54635 g/cm3  // 488.951 g  // 8.81573 cL  // 1 atm // 293.15 K
[Summary ->  · B00000B  // 0 daugh. // 5.54635 g/cm3  // 700.096 g  // 1.26227 dL  // 1 atm // 293.15 K
...
[Summary ->  · wlsr_ttx // 1 daugh. // 350 mg/cm3 // 1.15983 kg // 3.3138 L   // 1 atm // 293.15 K
[Summary ->  · world    // 1 daugh. // 1e-22 mg/cm3 // 154028 kg // 1.54028e+18 km3 // 3e-18 Pa  // 2.73 K
[Summary ->
[Summary -> Total: 171 volumes

Checking geometry¶

Tip

As seen above, the Geant4 overlap checker is enabled by default if GDML input is provided. It can be disabled with the /RMG/Geometry/GDMLDisableOverlapCheck command.

Apart from the on-by-default builtin overlap checking, remage provides a means to perform additional geometry checks that go beyond. For this it will be checking the integraity of the volume hierarchy along random geantino paths, and verify that the geometry navigator is always never mis-navigating the implemented hierarchy.

The user has to initialize this test in a specialized macro, that needs to be adapted to the geometry dimensions:

/RMG/Output/ActivateOutputScheme GeometryCheck

/run/initialize

/RMG/Generator/Confine Volume
/RMG/Generator/Confinement/SampleOnSurface
/RMG/Generator/Confinement/FirstSamplingVolume Geometrical

/RMG/Generator/Confinement/Geometrical/AddSolid Box
/RMG/Generator/Confinement/Geometrical/CenterPositionX 0 m
/RMG/Generator/Confinement/Geometrical/CenterPositionY 0 m
/RMG/Generator/Confinement/Geometrical/CenterPositionZ 0 m
/RMG/Generator/Confinement/Geometrical/Box/XLength 10 m
/RMG/Generator/Confinement/Geometrical/Box/YLength 10 m
/RMG/Generator/Confinement/Geometrical/Box/ZLength 10 m

/RMG/Generator/Select GPS
/gps/particle     geantino
/gps/energy       1 MeV
/gps/ang/type     iso

/run/beamOn {n}

The sampling surface has to be adjusted so that it lies fully within a single volume and also fully contains all daughter volumes of that volume, otherwise the check will not be correctly performed.