Volume filters

These are a set of filters that accept tracks under one of the following conditions

• In: particle is in a volume

• Enter: particle is entering a volume. AcceptTrack method returns always false

• Exit: particle is exiting a volume. AcceptTrack method returns always false, except in the case where one of the selected volumes is the world and track is exiting it

• Traverse: particle traverses a volume, it does neither enter nor exits it

• Start: particle is starting in a volume. AcceptTrack method may only return true if it is the first step

• End: particle is ending in a volume. AcceptTrack method may only return true if the track is ending

The volume names are given as extra parameters to the filter. The types of volume are the following ones

• LogicalVolume: a G4LogicalVolume object

• PhysicalVolume: a G4VPhysicalVolume object. The volume name and copy number are set separated with a ':' character, e.g. volA:1 (see section on Identifying touchables)

• PhysicalVolumeReplicated: for optimisation reasons the PhysicalVolume filters use the pointers to the physical volumes to find them. But in the case of replicated physical volumes (i.e. divisions, replicas and parameterisations), there is a unique PhysicalVolume pointer, while the different copies are managed internally by Geant4. Therefore you cannot select only a few of the copies of a physical volume with the above filters. For these cases you should use the PhysicalVolumeReplicated filters.

• Touchable: a G4VTouchable object. The volume name and copy number are set separated with a ':' character, the ancestors are separated by a '/' character, e.g. volB:3/volA:1 (see section on Identifying touchables)

• Region: a G4Region object

• LogicalVolumeChildren: a G4LogicalVolume object or any of the G4LogicalVolume children of it

• PhysicalVolumeChildren: a G4VPhysicalVolume object or any of the G4VPhysicalVolume children of it

• PhysicalVolumeReplicatedChildren: please read the discussion about PhysicalVolumeReplicated

• RegionChildren: a G4VTouchable object or any of the G4VTouchable children of it

• TouchableChildren: a G4Region object or any of the G4Region children of it

The name of these filters is constructed combining the geometry condition and the volume type, e.g. GmInPhysicalVolumeFilter, GmTraverseTouchableFilter, GmEndRegionFilter, GmTraverseLogicalVolumeChildrenFilter, GmExitRegionChildrenFilter.

There is a special case when parallel worlds are used: the scorers see the parallel world volumes, but the user actions do not. This means that you cannot use the above filters on a parallel world volume if you are using the filter for a user action, while you can if you use it for a scorer. If you want to do it you have to use the special parallel filters, namely

• EndParallelLogicalVolumeFilter

• EndParallelPhysicalVolumeFilter

• EndParallelPhysicalVolumeReplicatedFilter

• EndParallelRegionFilter

• EnterParallelLogicalVolumeFilter

• EnterParallelPhysicalVolumeFilter

• EnterParallelPhysicalVolumeReplicatedFilter

• EnterParallelRegionFilter

• ExitParallelLogicalVolumeFilter

• ExitParallelPhysicalVolumeFilter

• ExitParallelPhysicalVolumeReplicatedFilter

• ExitParallelRegionFilter

• InParallelLogicalVolumeFilter

• InParallelPhysicalVolumeFilter

• InParallelPhysicalVolumeReplicatedFilter

• InParallelRegionFilter

• StartParallelLogicalVolumeFilter

• StartParallelPhysicalVolumeFilter

• StartParallelPhysicalVolumeReplicatedFilter

• StartParallelRegionFilter

• TraverseParallelLogicalVolumeFilter

• TraverseParallelPhysicalVolumeFilter

• TraverseParallelPhysicalVolumeReplicatedFilter

• TraverseParallelRegionFilter

And it also means that you cannot use the above filters to act on a mass world whose position coincides with the one of a parallel world in the case of scorers, because the scorer filter will see the parallel world volume instead of the mass one. If you need to filter on mass volumes for a scorer a few volume filters are implemented, namely GmInMassLogicalVolumeFilter, GmInMassPhysicalVolumeFilter, GmInMassPhysicalVolumeReplicatedFilter and GmInMassRegionFilter.

When you use for example GmExitLogicalVolumeFilter the step is accepted when it exits the selected volume, without looking if the next volume it is entering is another copy of the selected volume. If what you want is that the steps are only accepted when they exit the selected volume and enter a different one, you may use the a filter that checks that if the PreStepPoint and the PostStepPoint are in different logical volumes:

• GmDifferentLogicalVolumeFilter

Although you may use the inverse of this filter to check if the two volumes are the same, GAMOS provides explicitly this filter:

• GmSameLogicalVolumeFilter