Description

This example allows the study of G4 cross-sections, and in addition, of the FLUKA hadron-nucleus reaction cross sections.

The user can printout any particle-material XS.
The XS are exactly the ones defined in any G4 physicsList chosen by the user, or from FLUKA (hadron-nucleus inelastic case).

In the input file, the user can set:

projectile.
target material (element, compound or even mixture).
plotting options.

All plots (created via the G4 analysis manager) can be dumped to any of the usually supported formats (e.g. ROOT format), but also in a Flair-compatible format.
Regarding the extension of G4H1 to insure Flair compatibility, see geant4/examples/extended/hadronic/FlukaCern/utils.

Note that the Geant4 SERIAL run manager is used, since FLUKA is single-threaded
(in actual FLUKA runs, parallelism is achieved via a multi-processing approach).

Before you can access the FLUKA hadron-nucleus inelastic model in this example, you will need to install and setup FLUKA and its interface.
See "Dependencies" paragraph below.

A version of the interface to FLUKA is directly located at geant4/examples/extended/hadronic/FlukaCern/FlukaInterface.

Dependencies

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 build / run a G4 application with the FLUKA interface.

Build this example

cd geant4/examples/extended/hadronic/FlukaCern/ProcessLevel/CrossSection/
# Check with `which fluka` that fluka executable is added to your `PATH`.
source path_to_geant4/install/bin/geant4.sh
source ../../FlukaInterface/env_FLUKA_G4_interface.sh
mkdir build
cd build
cmake3 -DG4_USE_FLUKA=1 ..
make -j8

Run this example

cd geant4/examples/extended/hadronic/FlukaCern/ProcessLevel/CrossSection/
# Check with `which fluka` that fluka executable is added to your `PATH`.
source path_to_geant4/install/bin/geant4.sh
source ../../FlukaInterface/env_FLUKA_G4_interface.sh
# Edit all_XS.in (choice of particle, material, energy range...)
# XS used by FTFP_BERT_HP physics list:
./build/HadronNucleusXS all_XS.in FTFP_BERT_HP
# XS used by G4_HP_CernFLUKAHadronInelastic_PhysicsList physics list:
./build/HadronNucleusXS all_XS.in G4_HP_CFLUKAHI

Study the cross-sections

All plots are dumped at the end of the run in all_XS.ext.

2 formats are supported: ROOT and Flair.

You can use ROOT:

cd geant4/examples/extended/hadronic/FlukaCern/ProcessLevel/CrossSection/
root all_XS.root

Alternatively, the use of Flair is also supported.

Please see http://flair.web.cern.ch/flair/download.html for Flair download.
Flair tutorials are also available from that website.
You can download the package corresponding to your distribution at the top of the page (no need for geoviewer, which is for geometry display). Then look at the requirements & installation instructions at the bottom of the page.

If you face issues installing Flair, you can get support at: https://fluka-forum.web.cern.ch/c/installation/

An example file, showing how to directly visualize all XS with Flair, is provided in this G4 example.
By default, it directly provides comparison plots:
FTFP_BERT_HP versus G4_HP_CernFLUKAHadronInelastic.
One can very easily adapt it (directly from Flair GUI) to any study of interest.
```
cd geant4/examples/extended/hadronic/FlukaCern/ProcessLevel/CrossSection/
mkdir -p results/FTFP_BERT_HP results/G4_HP_CernFLUKAHadronInelastic
# First run the example for FTFP_BERT, G4_HP_CernFLUKAHadronInelastic, and move the results!
./build/HadronNucleusXS all_XS.in FTFP_BERT_HP
mv all_XS.hist results/FTFP_BERT_HP
./build/HadronNucleusXS all_XS.in G4_HP_CFLUKAHI
mv all_XS.hist results/G4_HP_CernFLUKAHadronInelastic

flair study_all_XS.flair &
```
In the Plot tab, you can select the plot of interest in the left column, and then click Plot (top banner, yellow button).
You can select a physics list by clicking on its name in the Detectors box (center). You can then decide to change its color, line width (Options box). You can decide to plot it or not, by selecting / unselecting graph in the Show box (in the center).
You can change the path of the data file by clicking on the folder button (button on the right).
You can set the plots extrema, as well as select or unselect the log format, in the top right corner.