Remove multiple scattering from Processes

app/demo-geant-integration/NoFieldAlongStepFactory.cc

@@ -10,8 +10,10 @@
 #include <memory>
 #include <type_traits>
 
+#include "celeritas/em/msc/UrbanMscParams.hh"
 #include "celeritas/global/alongstep/AlongStepGeneralLinearAction.hh"
 #include "celeritas/io/ImportData.hh"
+#include "celeritas/phys/ImportedProcessAdapter.hh"
 
 namespace demo_geant
 {
@@ -22,12 +24,12 @@ namespace demo_geant
 auto NoFieldAlongStepFactory::operator()(argument_type input) const
     -> result_type
 {
-    // Create along-step action
     return celeritas::AlongStepGeneralLinearAction::from_params(
         input.action_id,
         *input.material,
         *input.particle,
-        *input.physics,
+        celeritas::UrbanMscParams::from_import(
+            *input.particle, *input.material, *input.imported),
         input.imported->em_params.energy_loss_fluct);
 }
 

app/demo-loop/LDemoIO.cc

@@ -16,6 +16,7 @@
 #include "corecel/io/StringUtils.hh"
 #include "corecel/sys/Device.hh"
 #include "celeritas/Units.hh"
+#include "celeritas/em/msc/UrbanMscParams.hh"
 #include "celeritas/ext/GeantImporter.hh"
 #include "celeritas/ext/GeantPhysicsOptionsIO.json.hh"
 #include "celeritas/ext/GeantSetup.hh"
@@ -272,14 +273,16 @@ TransporterInput load_input(LDemoArgs const& args)
     }
 
     bool eloss = imported_data.em_params.energy_loss_fluct;
+    auto msc = UrbanMscParams::from_import(
+        *params.particle, *params.material, imported_data);
     if (args.mag_field == LDemoArgs::no_field())
     {
         // Create along-step action
         auto along_step = AlongStepGeneralLinearAction::from_params(
             params.action_reg->next_id(),
             *params.material,
             *params.particle,
-            *params.physics,
+            msc,
             eloss);
         params.action_reg->insert(along_step);
     }
@@ -298,8 +301,8 @@ TransporterInput load_input(LDemoArgs const& args)
             f *= units::tesla;
         }
 
-        auto along_step = AlongStepUniformMscAction::from_params(
-            params.action_reg->next_id(), *params.physics, field_params);
+        auto along_step = std::make_shared<AlongStepUniformMscAction>(
+            params.action_reg->next_id(), field_params, msc);
         CELER_ASSERT(along_step->field() != LDemoArgs::no_field());
         params.action_reg->insert(along_step);
     }

src/celeritas/CMakeLists.txt

@@ -40,13 +40,12 @@ list(APPEND SOURCES
   em/model/RayleighModel.cc
   em/model/RelativisticBremModel.cc
   em/model/SeltzerBergerModel.cc
-  em/model/UrbanMscModel.cc
+  em/msc/UrbanMscParams.cc
   em/process/BremsstrahlungProcess.cc
   em/process/ComptonProcess.cc
   em/process/EIonizationProcess.cc
   em/process/EPlusAnnihilationProcess.cc
   em/process/GammaConversionProcess.cc
-  em/process/MultipleScatteringProcess.cc
   em/process/PhotoelectricProcess.cc
   em/process/RayleighProcess.cc
   geo/GeoMaterialParams.cc

src/celeritas/Types.hh

@@ -144,6 +144,15 @@ struct NoData
 {
 };
 
+//! Within-kernel state for step limits and action
+struct AlongStepLocalState
+{
+    //! Final step limit (true path length) and action
+    StepLimit step_limit;
+    //! Smooth (straight/curved) step movement without accounting for MSC
+    real_type geo_step{};
+};
+
 //---------------------------------------------------------------------------//
 // HELPER FUNCTIONS (HOST)
 //---------------------------------------------------------------------------//

src/celeritas/em/data/UrbanMscData.hh

@@ -18,7 +18,7 @@ namespace celeritas
 {
 //---------------------------------------------------------------------------//
 /*!
- * UrbanMscModel settable parameters and default values.
+ * Settable parameters and default values for Urban multiple scattering.
  *
  * \f$ \tau = t/\lambda \f$ where t is the true path length and \f$ \lambda \f$
  * is the mean free path of the multiple scattering. The range and safety
@@ -92,19 +92,18 @@ struct UrbanMscMaterialData
 //---------------------------------------------------------------------------//
 /*!
  * Physics IDs for MSC.
+ *
+ * TODO these will probably be changed to a map over all particle IDs.
  */
 struct UrbanMscIds
 {
-    // TODO: remove when this is no longer a model
-    ActionId action;
-    // TODO: change to a bitset based on particle ID when we add muons, hadrons
     ParticleId electron;
     ParticleId positron;
 
     //! Whether the IDs are assigned
     explicit CELER_FUNCTION operator bool() const
     {
-        return action && electron && positron;
+        return electron && positron;
     }
 };
 
@@ -151,7 +150,7 @@ struct UrbanMscData
 
     //// DATA ////
 
-    //! Type-free IDs
+    //! Particle IDs
     UrbanMscIds ids;
     //! Mass of of electron in MeV
     units::MevMass electron_mass;

src/celeritas/global/alongstep/detail/UrbanMsc.hh → src/celeritas/em/msc/UrbanMsc.hh

@@ -3,7 +3,7 @@
 // See the top-level COPYRIGHT file for details.
 // SPDX-License-Identifier: (Apache-2.0 OR MIT)
 //---------------------------------------------------------------------------//
-//! \file celeritas/global/alongstep/detail/UrbanMsc.hh
+//! \file celeritas/em/msc/UrbanMsc.hh
 //---------------------------------------------------------------------------//
 #pragma once
 
@@ -12,9 +12,10 @@
 #include "corecel/Types.hh"
 #include "celeritas/Types.hh"
 #include "celeritas/em/data/UrbanMscData.hh"
-#include "celeritas/em/distribution/UrbanMscScatter.hh"
-#include "celeritas/em/distribution/UrbanMscStepLimit.hh"
-#include "celeritas/global/alongstep/AlongStep.hh"
+#include "celeritas/global/CoreTrackView.hh"
+
+#include "UrbanMscScatter.hh"
+#include "UrbanMscStepLimit.hh"
 
 namespace celeritas
 {
@@ -124,7 +125,7 @@ CELER_FUNCTION void UrbanMsc::calc_step(CoreTrackView const& track,
         // TODO: this is already kinda sorta determined inside the
         // UrbanMscStepLimit calculation
         local->step_limit.step = msc_step_result.true_path;
-        local->step_limit.action = msc_params_.ids.action;
+        local->step_limit.action = phys.scalars().msc_action();
     }
 }
 

src/celeritas/em/distribution/UrbanMscHelper.hh → src/celeritas/em/msc/UrbanMscHelper.hh

@@ -3,7 +3,7 @@
 // See the top-level COPYRIGHT file for details.
 // SPDX-License-Identifier: (Apache-2.0 OR MIT)
 //---------------------------------------------------------------------------//
-//! \file celeritas/em/distribution/UrbanMscHelper.hh
+//! \file celeritas/em/msc/UrbanMscHelper.hh
 //---------------------------------------------------------------------------//
 #pragma once