Using optical map¶

Warning

Work in progress, more will be added later! reboost-optical is also not integrated with the remaining reboost stack.

Creating optical maps¶

1. Running remage simulations to get stp file¶

The map generation is performed directly with remage(reboost is not involved in this step). An example macro to showcase the required settings (map.mac):

/RMG/Processes/OpticalPhysics true
/RMG/Processes/OpticalPhysicsMaxOneWLSPhoton true

/RMG/Geometry/RegisterDetectorsFromGDML Optical

/RMG/Geometry/GDMLDisableOverlapCheck true

/run/initialize

/RMG/Output/NtuplePerDetector false
/RMG/Output/Vertex/StorePrimaryParticleInformation false
/RMG/Output/Vertex/StoreSinglePrecisionEnergy true
/RMG/Output/Vertex/StoreSinglePrecisionPosition true

# confinement in disk around array
/RMG/Generator/Confine Volume

/RMG/Generator/Confinement/SamplingMode IntersectPhysicalWithGeometrical
/RMG/Generator/Confinement/ForceContainmentCheck true

/RMG/Generator/Confinement/Physical/AddVolume lar

/RMG/Generator/Confinement/Geometrical/AddSolid Cylinder
/RMG/Generator/Confinement/Geometrical/CenterPositionX 0 m
/RMG/Generator/Confinement/Geometrical/CenterPositionY 0 m
/RMG/Generator/Confinement/Geometrical/CenterPositionZ 0.69 m
/RMG/Generator/Confinement/Geometrical/Cylinder/InnerRadius 0 m
/RMG/Generator/Confinement/Geometrical/Cylinder/OuterRadius 0.7 m
/RMG/Generator/Confinement/Geometrical/Cylinder/Height 2.4 m

/RMG/Generator/Select GPS
/gps/particle     opticalphoton
/gps/ene/type     Gauss
/gps/ene/mono     9.68 eV # 128nm (VUV) LAr scintillation
/gps/ene/sigma    0.22 eV # gaussian width
/gps/ang/type     iso
# use random polariztation (this emits warnings that can be ignored)
#/gps/polarization 1 1 1

/run/beamOn 80000000

Run remage with this macro to produce the (flat) output file:

$ remage -g l200-geometry.gdml -o map.stp.lh5 --flat-output -- map.mac

2. Convert stp to evt file¶

Convert the step table output from remage to a more efficiently iterable form:

$ reboost-optical evt --detectors detectors.json map.stp.lh5 map.evt.lh5

Note

this step might be replaced with GLM iteration in the future.

the evt step can be very well parallelized by just running it in parallel for different files. memory usage for each process should be minimal.

3. Create the map¶

with a map settings file (map-settings.json):

{
  "range_in_m": [
    [-0.7, 0.7],
    [-0.7, 0.7],
    [-0.51, 1.89]
  ],
  "bins": [280, 280, 480]
}

a list of the optical detector uids has to be provided in a second JSON file (detectors.json):

[1052802, 1052803 /* ... */]

$ reboost-optical createmap --settings map-settings.json --detectors detectors.json map.evt.lh5 map.map.lh5

createmap can also work on multiple input files at once. Make sure that enough memory is available; the map object is fully stored in memory. In this example: For the 58 hardware channels, the example above would require

\[\text{memory} = 8 \cdot n_x \cdot n_y \cdot n_z \cdot (n_\text{ch} + 4) = 8 \cdot 280 \cdot 280 \cdot 480 \cdot (58 + 4) = 19\times10^{9} \text{[bytes]}\]

but peak memory usage might be higher. The input buffer will also use some memory.

For parallelization, createmap supports a -N <n_cpu> argument. However, this cannot be scaled indefinitely. Be aware of the memory configuration of the compute node used (i.e., performance may suffer when using more processors than in a NUMA domain). createmap internally uses locks to access one shared memory instance of the to-be-created map. The more CPUs are used for the task, the more lock contention might happen.

Note

In practice, a specific scheme has been shown to be working for large LEGEND maps. 16 cores on a NERSC perlmutter node work quite fine to produce a map from a set of input files. To use more of the available resources, 256 input files are used for one createmap task; up to 16 (typically only 12 to have some spare memory for the peaks) such tasks are run in parallel. This means a total of 4096 remage output files can be read in parallel.

The 12-16 output files can then be combined into one with

$ reboost-optical mergemap --settings map-settings.json map.map*.lh5 final-output-map.lh5

Applying optical maps to physics simulations¶

Important

reboost-optical is not yet integrated with the remaining reboost stack. The optical response can be generated with the standalone command reboost-optical convolve.

reboost-optical currently does not support the recent changes in remage output format. It currently only works when the following macro commands are set:

/RMG/Output/Scintillator/StoreParticleVelocities
/RMG/Output/Scintillator/StepPositionMode Both
/RMG/Output/Scintillator/Cluster/PreClusterOutputs false

If the liquid argon volume is registered as a Scintillator detector with uid 1, the optical response can be created with:

reboost-optical convolve --material lar --map map.lh5 --edep remage-output.lh5 --edep-lgdo /stp/det001 --output optical-response.lh5