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LBNE Geometries

There are two different 35t prototype geometries and several FD-relevant geometries in the repository, accessible through the lbne35t_geo and lbne10kt_geo art parameter sets, respectively. In short, the different files are:

  • lbne35t.gdml -- The old 3-APA design for the 35t prototype
  • lbne35t4apa.gdml -- The new 4-APA design for the 35t prototype
  • lbne10kt.gdml -- standard FD design; 2 Cryostats side-by-side, 3x2x10 APAs in each, at the surface
  • lbne34kt.gdml -- larger design; 2 Cryostats end-to-end, 3x2x18 APAs in each with a longer drift
  • lbne10kt_APAoutside.gdml -- different FD design proposal fitting an extra anode plane in the same volume
  • lbne4apa36deg.gdml -- FD-sized apas, but only 4 of them in a single cryostat with minimally sized world volume
  • lbne4apa45deg.gdml -- Same as above but with U/V wires at about 45deg instead of 36deg.

Selecting Specific Geometry Files

LArSoft has 2 LBNE geometry configurations throughout the all of the fcl files, defined in Geometry/geometry_lbne.fcl. Here, parameter sets lbnefd_geo and lbne35t_geo are defined with a specific gdml file path, a geometry name, a distance from the surface, and a switch to use a file with no wires in Geant4. While the name should be left the same, the path to the gdml file can be changed to select from several options. For example, the code below has selected not the full geometry, but a mini-version for use in day-to-day software development. Note that the name doesn't really need to change unless the channel map, or some other detector ID specific code, cannot be general to kLBNE10kt and the needed functionality at the same time. So far, however, all of the lbnefd_geo geometry files work exactly the same way in LArSoft.

lbnefd_geo:
{
 Name:     "lbne10kt" 

 # Choose GDML file
 #GDML:     "Geometry/gdml/lbne10kt.gdml" 
 #ROOT:     "Geometry/gdml/lbne10kt.gdml" 
 #GDML:     "Geometry/gdml/lbne10kt_APAoutside.gdml" 
 #ROOT:     "Geometry/gdml/lbne10kt_APAoutside.gdml" 
 GDML:     "Geometry/gdml/lbne4apa36deg.gdml"   # *45deg.gdml or *36deg.gdml
 ROOT:     "Geometry/gdml/lbne4apa36deg.gdml" 

 SurfaceY:           0.0e2               #in cm, vertical distance to the surface
 DisableWiresInG4:   true
}

Aiming Events In A Geometry

The GeometryTest module has a method named printVolBounds which is commented out by default. Uncomment this and run GeometryTest on whatever geometry you want to generate in -- this will print out cryostat and TPC boundaries in world coordinates. Note that the wire planes are slightly smaller in y-z than the TPC volume, though the TPCActive y-z boundaries are equal to the its corresponding wire plane y-z boundaries.

35t Prototype Geometry

The lbne35t.gdml file is old and should only be used to look at files generated before the design change. The lbne35t4apa.gdml file describes the new 35t geometry with 4 slimmer APAs; this is drawn in the image below without any wires. Drawn are the APA frames (dark grey), CPAs (burnt orange), vertical optical detectors (blue/purple), and 8 imaginary active volume bounds (light grey). The coordinate system is also overlaid in red, with the origin placed as follows:

  • x=0 is the +x face of the first wire plane (U, there is no grid plane in gdml) in the largest drift volume
  • y=0 halves the space between the top and bottom center APAs
  • z=0 is the front face of the active volume

Far Detector Geometry

The standard full file for Far Detector geometry is lbne10kt or lbne34kt. At the time of writing, the only differences are that 34kt has a longer drift distance, 18 sets of APAs adjacent in the z direction, and cryostats end-to-end instead of side-by-side. Another proposed geometry, with 4 planes of APAs per cryostat has also been checked in with the name lbne10kt_APAoutside.gdml. In all of these geometries, the origin is placed as follows:

  • x=0 the center of the cryostat for lbne34kt, and in the middle of the 2 cryostats in lbne10kt and lbne10kt_APAoutside
  • y=0 halves the space between the top and bottom APAs
  • z=0 is the front face of the active volume.

Here are images of the 34kt, 10kt, and 10kt_APAoutside geometries, respectively. Drawn are many CPAs (burnt orange), optical detectors (blue/purple), the cryostat shells (dark grey), and the TPCActive volumes (light grey). Wires are not drawn, but APAs can be imagined to hold the drawn optical detectors.

34kt: 216 APAs, 288 CPAs, 432 volTPCs

10kt: 120 APAs, 160 CPAs, 240 volTPCs -- note that this is also available with U/V wires at 36 degrees from vertical as well (lbne10kt36.gdml)

10kt_APAoutside: 160 APAs, 120-200 CPAs (??), 320 volTPCs, though the outer ones would be treated differently.

Far Detector Workspace

Events generated/reconstructed in the above FD geometry files, however, take significant amounts of time and memory when using LArSoft, potentially making day-to-day development using these files impractical. If working with this, be sure to try out the optimized version of LArSoft when setting up your environment . The size of a simulated root file will be scaled by the number of channels (and number of photons if running optical simulation), so a geometry with many APAs is going to be unnecessarily cumbersome. For trying out new algorithms and simulations, it would be most practical to start out in a geometry with as few APAs as possible that still had vertical and horizontal gaps in active drift volume -- so there is a geometry with 2 APAs high by 2 APAs long (beam direction). Also, given the continued discussion of altering wire angle to optimize disambiguation, and given the aspect ratio of the current FD APA design (2.5x7), this 4 APA geometry is available with wrapped wires at 36 degrees from vertical (lbne4apa36deg). There are also 10 optical detectors per APA.

This is sufficient for development until we start to link up muon tracks across many APAs, most likely beginning with solid 3D information.

35t GDML