extend Steps ntuple and switch Docker to Geant4 submodule source

Add 15 new columns to the Steps ntuple: edep, step_length, parent_id,
process name, layer_id, material, pre-step momentum direction, and
B/E field components (in T and V/m) at the pre-step point.

Replace wget Geant4 tarball download in all three Dockerfiles with
ADD of the lib/geant4 submodule source; narrow submodule init to
lib/pybind11 only so builds no longer require network access for Geant4.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/RunAction.cc

@@ -95,7 +95,22 @@ RunAction::RunAction()
   analysisManager->CreateNtupleDColumn("post_x");     // col 8
   analysisManager->CreateNtupleDColumn("post_y");     // col 9
   analysisManager->CreateNtupleDColumn("post_z");     // col 10
-  analysisManager->CreateNtupleDColumn("post_E");     // col 11
+  analysisManager->CreateNtupleDColumn("post_E");      // col 11
+  analysisManager->CreateNtupleDColumn("edep");        // col 12 [MeV]
+  analysisManager->CreateNtupleDColumn("step_length"); // col 13 [mm]
+  analysisManager->CreateNtupleIColumn("parent_id");   // col 14
+  analysisManager->CreateNtupleSColumn("process");     // col 15
+  analysisManager->CreateNtupleIColumn("layer_id");    // col 16  (-1 = outside all layers)
+  analysisManager->CreateNtupleSColumn("material");    // col 17
+  analysisManager->CreateNtupleDColumn("pre_dx");      // col 18
+  analysisManager->CreateNtupleDColumn("pre_dy");      // col 19
+  analysisManager->CreateNtupleDColumn("pre_dz");      // col 20
+  analysisManager->CreateNtupleDColumn("Bx");          // col 21 [T]
+  analysisManager->CreateNtupleDColumn("By");          // col 22 [T]
+  analysisManager->CreateNtupleDColumn("Bz");          // col 23 [T]
+  analysisManager->CreateNtupleDColumn("Ex");          // col 24 [V/m]
+  analysisManager->CreateNtupleDColumn("Ey");          // col 25 [V/m]
+  analysisManager->CreateNtupleDColumn("Ez");          // col 26 [V/m]
   analysisManager->FinishNtuple();
 }
 

src/SteppingAction.cc

@@ -36,6 +36,10 @@
 #include "G4AnalysisManager.hh"
 #include "G4Track.hh"
 #include "G4ParticleDefinition.hh"
+#include "G4TransportationManager.hh"
+#include "G4FieldManager.hh"
+#include "G4Field.hh"
+#include "G4SystemOfUnits.hh"
 
 using namespace B4;
 
@@ -95,6 +99,63 @@ void SteppingAction::UserSteppingAction(const G4Step* step)
   analysisManager->FillNtupleDColumn(1, 9, post->GetPosition().y());
   analysisManager->FillNtupleDColumn(1, 10, post->GetPosition().z());
   analysisManager->FillNtupleDColumn(1, 11, post->GetKineticEnergy());
+
+  // A: energy deposited in medium at this step (≠ pre_E - post_E when secondaries are created)
+  analysisManager->FillNtupleDColumn(1, 12, edep);
+
+  // B: geometric step length
+  analysisManager->FillNtupleDColumn(1, 13, step->GetStepLength());
+
+  // C: parent track ID (0 for primary)
+  analysisManager->FillNtupleIColumn(1, 14, track->GetParentID());
+
+  // D: process that ended this step
+  G4String processName = "";
+  const auto* postProc = post->GetProcessDefinedStep();
+  if (postProc) processName = postProc->GetProcessName();
+  analysisManager->FillNtupleSColumn(1, 15, processName);
+
+  // E: layer index (-1 if outside all layers) and material name at pre-step point
+  int layerId = -1;
+  const auto& layers = cw->getLayers();
+  for (int i = 0; i < (int)layers.size(); i++) {
+    if (layers[i].physicalVolume == volume) { layerId = i; break; }
+  }
+  G4String materialName = pre->GetMaterial() ? pre->GetMaterial()->GetName() : "";
+  analysisManager->FillNtupleIColumn(1, 16, layerId);
+  analysisManager->FillNtupleSColumn(1, 17, materialName);
+
+  // F: pre-step momentum direction (unit vector)
+  const auto dir = pre->GetMomentumDirection();
+  analysisManager->FillNtupleDColumn(1, 18, dir.x());
+  analysisManager->FillNtupleDColumn(1, 19, dir.y());
+  analysisManager->FillNtupleDColumn(1, 20, dir.z());
+
+  // Field: B [T] and E [V/m] at pre-step position; zero if no field is registered
+  G4double Bx=0, By=0, Bz=0, Ex=0, Ey=0, Ez=0;
+  const auto* fm = G4TransportationManager::GetTransportationManager()->GetFieldManager();
+  if (fm && fm->DoesFieldExist()) {
+    const G4Field* field = fm->GetDetectorField();
+    if (field) {
+      const G4double point[4] = {pre->GetPosition().x(), pre->GetPosition().y(),
+                                  pre->GetPosition().z(), pre->GetGlobalTime()};
+      G4double fieldVal[6] = {0,0,0,0,0,0};
+      field->GetFieldValue(point, fieldVal);
+      Bx = fieldVal[0] / tesla;
+      By = fieldVal[1] / tesla;
+      Bz = fieldVal[2] / tesla;
+      Ex = fieldVal[3] / (volt/m);
+      Ey = fieldVal[4] / (volt/m);
+      Ez = fieldVal[5] / (volt/m);
+    }
+  }
+  analysisManager->FillNtupleDColumn(1, 21, Bx);
+  analysisManager->FillNtupleDColumn(1, 22, By);
+  analysisManager->FillNtupleDColumn(1, 23, Bz);
+  analysisManager->FillNtupleDColumn(1, 24, Ex);
+  analysisManager->FillNtupleDColumn(1, 25, Ey);
+  analysisManager->FillNtupleDColumn(1, 26, Ez);
+
   analysisManager->AddNtupleRow(1);
 }