feat: Geant4 kill particle after configurable time (#2097)

This adds an option to the particle killer to kill a particle after a certain time. Also applies this feature to the full-chain-example of the ODD with a (hopefully) reasonable value of 25ns.

Co-authored-by: Andreas Stefl <487211+andiwand@users.noreply.github.com>

Examples/Algorithms/Geant4/include/ActsExamples/Geant4/ParticleKillAction.hpp

@@ -28,6 +28,7 @@ class ParticleKillAction : public G4UserSteppingAction {
   /// Configuration of the Stepping action
   struct Config {
     std::shared_ptr<const Acts::Volume> volume;
+    double maxTime = std::numeric_limits<double>::infinity();
   };
 
   /// Construct the stepping action

Examples/Algorithms/Geant4/src/ParticleKillAction.cpp

@@ -25,14 +25,22 @@ ActsExamples::ParticleKillAction::ParticleKillAction(
 
 void ActsExamples::ParticleKillAction::UserSteppingAction(const G4Step* step) {
   constexpr double convertLength = Acts::UnitConstants::mm / CLHEP::mm;
+  constexpr double convertTime = Acts::UnitConstants::ns / CLHEP::ns;
+
   G4Track* track = step->GetTrack();
 
   const auto pos = convertLength * track->GetPosition();
+  const auto time = convertTime * track->GetGlobalTime();
+
+  const bool outOfVolume =
+      m_cfg.volume and
+      not m_cfg.volume->inside(Acts::Vector3{pos.x(), pos.y(), pos.z()});
+  const bool outOfTime = time > m_cfg.maxTime;
 
-  if (m_cfg.volume and
-      not m_cfg.volume->inside(Acts::Vector3{pos.x(), pos.y(), pos.z()})) {
-    ACTS_DEBUG("Kill track with internal track ID " << track->GetTrackID()
-                                                    << " at " << pos);
+  if (outOfVolume or outOfTime) {
+    ACTS_DEBUG("Kill track with internal track ID "
+               << track->GetTrackID() << " at " << pos << " and global time "
+               << time / Acts::UnitConstants::ns << "ns");
     track->SetTrackStatus(G4TrackStatus::fStopAndKill);
   }
 }

Examples/Python/python/acts/examples/simulation.py

@@ -476,7 +476,6 @@ def addSimWriters(
     particlesInitial="particles_initial",
     particlesFinal="particles_final",
 ) -> None:
-
     customLogLevel = acts.examples.defaultLogging(s, logLevel)
 
     if outputDirCsv is not None:
@@ -577,6 +576,7 @@ def addGeant4(
     outputDirRoot: Optional[Union[Path, str]] = None,
     logLevel: Optional[acts.logging.Level] = None,
     killVolume: Optional[acts.Volume] = None,
+    killAfterTime: float = float("inf"),
 ) -> None:
     """This function steers the detector simulation using Geant4
 
@@ -600,6 +600,8 @@ def addGeant4(
         the output folder for the Root output, None triggers no output
     killVolume: acts.Volume, None
         if given, particles are killed when going outside of this volume.
+    killAfterTime: float, None
+        if given, particle are killed after the global time since event creation exceeds the given value
     """
 
     from acts.examples.geant4 import Geant4Simulation, makeGeant4SimulationConfig
@@ -633,6 +635,7 @@ def addGeant4(
         volumeMappings=volumeMappings,
         materialMappings=materialMappings,
         killVolume=killVolume,
+        killAfterTime=killAfterTime,
         recordHitsOfSecondaries=recordHitsOfSecondaries,
         keepParticlesWithoutHits=keepParticlesWithoutHits,
     )

Examples/Python/src/Base.cpp

@@ -26,9 +26,8 @@ namespace Acts::Python {
 void addUnits(Context& ctx) {
   auto& m = ctx.get("main");
   auto u = m.def_submodule("UnitConstants");
-  using namespace Acts::UnitConstants;
 
-#define UNIT(x) u.attr(#x) = x;
+#define UNIT(x) u.attr(#x) = Acts::UnitConstants::x;
 
   UNIT(fm)
   UNIT(pm)

Examples/Python/src/Geant4Component.cpp

@@ -153,7 +153,7 @@ PYBIND11_MODULE(ActsPythonBindingsGeant4, mod) {
               magneticField,
           const std::vector<std::string>& volumeMappings,
           const std::vector<std::string>& materialMappings,
-          std::shared_ptr<const Acts::Volume> killVolume,
+          std::shared_ptr<const Acts::Volume> killVolume, double killAfterTime,
           bool recordHitsOfSecondaries, bool keepParticlesWithoutHits) {
         auto logger = Acts::getDefaultLogger("Geant4", level);
 
@@ -180,9 +180,9 @@ PYBIND11_MODULE(ActsPythonBindingsGeant4, mod) {
         steppingCfg.actions.push_back(new SensitiveSteppingAction(
             g4StepCfg, logger->cloneWithSuffix("SensitiveStepping")));
 
-        steppingCfg.actions.push_back(
-            new ParticleKillAction(ParticleKillAction::Config{killVolume},
-                                   logger->cloneWithSuffix("Killer")));
+        steppingCfg.actions.push_back(new ParticleKillAction(
+            ParticleKillAction::Config{killVolume, killAfterTime},
+            logger->cloneWithSuffix("Killer")));
 
         g4Cfg.steppingAction = new ActsSteppingActionList(steppingCfg);
 
@@ -219,6 +219,7 @@ PYBIND11_MODULE(ActsPythonBindingsGeant4, mod) {
       py::arg("volumeMappings") = std::vector<std::string>{},
       py::arg("materialMappings") = std::vector<std::string>{},
       py::arg("killVolume") = nullptr,
+      py::arg("killAfterTime") = std::numeric_limits<double>::infinity(),
       py::arg("recordHitsOfSecondaries") = true,
       py::arg("keepParticlesWithoutHits") = true);
 

Examples/Scripts/Python/full_chain_odd.py

@@ -124,7 +124,8 @@
             outputDirRoot=outputDir,
             # outputDirCsv=outputDir,
             rnd=rnd,
-            killVolume=acts.Volume.makeCylinderVolume(r=1100, halfZ=3000),
+            killVolume=acts.Volume.makeCylinderVolume(r=1.1 * u.m, halfZ=3.0 * u.m),
+            killAfterTime=25 * u.ns,
         )
     else:
         addFatras(