This is an interface to the FLUKA CERN hadron inelastic physics.
It can be used by ANY G4 application (including the experimental frameworks, provided they are relying on G4 physics lists already).

Note that this is a generic guide to be able to use the FLUKA interface from any G4 application.
If you are trying to build / run the G4 examples included in FlukaCern with FLUKA,
please directly follow the README.md files included in
ProcessLevel/CrossSection and ProcessLevel/FinalState.

Description

The FLUKA hadron inelastic physics are accessible both through a CrossSectionDataSet and HadronicInteraction.
The CrossSectionDataSet and HadronicInteraction can be used to define processes, themselves used to form a FLUKAHadronInelasticPhysicsConstructor.
The FLUKAHadronInelasticPhysicsConstructor can in turn be used to form any G4PhysicsList. One example of G4PhysicsList is provided (initially FTFP_BERT_HP, but with hadron inelastic physics from FLUKA instead).
Note that for consistency, all calls to the random engine rely on the G4 random engine (including the calls from within the downloaded FLUKA release; see the FlukaInterface GNUmakefile to see how this is handled).

Structure

The project contains:

fluka4_wrapper: wrapper to FLUKA.
cpp_fortran_bridges: fortran <-> C++ interfacing tools.
cpp_utils: general project helpers (C++ string manipulation, etc).
fluka5: interface to FLUKA inelastic hadron-nucleus interactions.
fluka_G4_physics_list: ModularPhysicsList, PhysicsConstructor, CrossSectionDataSet, HadronicInteraction to make up a G4 physics list.
fluka_G4_bridges: conversion tools to switch between FLUKA and G4 worlds (particles, random numbers, etc).

Dependency

Environment

gcc >= 7 (Linux) and gcc >= 9 (MacOS)
In practice, a recent version is recommended, at least gcc >=10.

gcc --version

CMake >= 3.16...3.21

cmake3 --version

G4 >= 11.0.3 (Not tested on older G4 releases: might still work, but with no guarantee).
IMPORTANT: YOU NEED TO SOURCE YOUR G4 ENVIRONMENT. It needs to be sourced in whichever terminal you want to build / run a G4 application with the FLUKA interface.

source path_to_geant4/install/bin/geant4.sh
which geant4-config   # NB: Your geant4-config should support the modern CMake way of building G4.

Easy setup on lxplus (lxplus7):
All you need to do on lxplus, to setup an environment satisfying all the conditions above, is, for example:

source /cvmfs/sft.cern.ch/lcg/releases/gcc/10.1.0/x86_64-centos7/setup.sh
source /cvmfs/geant4.cern.ch/geant4/11.1/x86_64-centos7-gcc10-optdeb-MT/CMake-setup.sh
# NB: Your geant4.sh is at: /cvmfs/geant4.cern.ch/geant4/11.1/x86_64-centos7-gcc10-optdeb-MT/bin/geant4.sh

`FLUKA4`

Release: >= 4-3.2

Please install the latest FLUKA release.
(1) You first need to register (and accept the licence when relevant): https://fluka.cern/download/registration
(2) You can then download the binary libraries (or potentially the source code package, depending on your case):
https://fluka.cern/download/latest-fluka-release.
(3) Follow the FLUKA installation instructions: https://fluka.cern/documentation/installation
In particular, for a Linux/MacOS install: https://fluka.cern/documentation/installation/fluka-linux-macos
They will show you how to setup FLUKA.
If (and only if) you went for the source code package option, you will need to build fluka, and, in addition, to do make cpp_headers at path_to_fluka/src.
(4) Eventually, all you need are the headers fluka_repo/include, libraries fluka_repo/lib, and data fluka_repo/data. Check that they are not empty.
Do not forget to add /path_to_fluka/bin to your PATH. Check with which fluka.

`FlukaInterface`

A version of the G4-FLUKA interface (FLUKA hadron-nucleus inelastic physics) is located at geant4/examples/extended/hadronic/FlukaCern/FlukaInterface.
You will first need to build the interface to FLUKA, and create the environment scripts.

$ cd geant4/examples/extended/hadronic/FlukaCern/FlukaInterface/
# Check with `which fluka` that fluka executable is added to your `PATH`.
$ source path_to_geant4/install/bin/geant4.sh
$ make interface
$ make env       # Creates `env_FLUKA.sh` and `env_FLUKA_G4_interface.sh`

IMPORTANT: env_FLUKA_G4_interface.sh needs to be sourced in whichever terminal you want to compile / run a G4 application with the FLUKA interface.

Use as a FLUKA physics list (in ANY G4 application)

Reminder: this is a generic guide to be able to use the FLUKA interface from any G4 application.
If you are trying to build / run the G4 examples included in FlukaCern with FLUKA, you can directly follow the README.md files included in those examples.
Notably, the file in cmake/Modules is already included in those examples (the rest of the procedure is the same).

$ cd G4_application

Edit your G4 application's CMakeLists.txt:
You need to add the FLUKA module dependency. You need to add the following (for example, after the project line):

#----------------------------------------------------------------------------
# FindFLUKAInterface.cmake is located at your_path_to_geant4/cmake/Modules/FindFLUKAInterface.cmake
# Check that FindFLUKAInterface.cmake can be found from $CMAKE_MODULE_PATH
message(STATUS "CMAKE_MODULE_PATH = ${CMAKE_MODULE_PATH}")
# Otherwise, you can always prepend it to the cmake module search path with:
# set(CMAKE_MODULE_PATH my_path_to_find_fluka ${CMAKE_MODULE_PATH})

#----------------------------------------------------------------------------
# Check whether FLUKA should be used or not
set(G4_USE_FLUKA OFF CACHE BOOL "Using FLUKA")
if(G4_USE_FLUKA)
  message(STATUS "G4_USE_FLUKA=ON : Using FLUKA interface for building ${PROJECT_SOURCE_DIR}")
  add_definitions(-DG4_USE_FLUKA)
  find_package(FLUKAInterface REQUIRED)
  if(FLUKAInterface_FOUND)
    message(STATUS "FLUKA cmake module was found : ${CMAKE_MODULE_PATH}")
  else()
    message(FATAL_ERROR "FLUKA cmake module was NOT found! Please add one.")
  endif()
else()
  message(STATUS "G4_USE_FLUKA=OFF : NOT using FLUKA interface for building ${PROJECT_SOURCE_DIR}. \n \
  If ever you want to use the FLUKA interface, please repeat cmake command with -DG4_USE_FLUKA=1")
endif()

Additionally, add:
${FLUKAInterface_INCLUDE_DIR} to the include_directories line.
${FLUKAInterface_LIBRARIES} to the target_link_libraries line.

You can now compile and run your G4 application:

# Check with `which fluka` that fluka executable is added to your `PATH`.
$ source path_to_geant4/install/bin/geant4.sh
$ source path_to_FlukaInterface/env_FLUKA_G4_interface.sh             # Carefully follow the setup instructions if anything fails.
$ cd build
$ cmake3 -DGeant4_DIR=your_path_to_geant4 -DG4_USE_FLUKA=1 ../
$ make -j8
$ ./G4_executable

README.md

Interface to FLUKA physics models