Exercise to build and run a Geant4 simulation.

Transcription

1 Exercise to build and run a Geant4 simulation. The aim of this lecture is to build a running Geant4 Monte-Carlo application from source code. In the exercise, all the necessary steps to build, link and run a simulation will be presented step-by-step. The exercise is based on the already implemented Geant4 code called MaS1 which can be downloaded from Studentportalen. All Linux commands used for this exercise will be in Italic font in a step-by-step work flow. The normal terminal prompt under galactica will look like [username@node directory] There username is your username, node is the node you are logged into and directory is the current directory. Download files from Studentportalen Log in to one of the galactica nodes apollo.physics.uu.se starbuck.physics.uu.se adama.physics.uu.se roslin.physics.uu.se using putty or any other ssh client, see USER manual Galactica for students. In the terminal window you should see a prompt looking like [username@galactica ~] There ~indicate that you are in your home directory and galactica can be apollo, starbuck, adama or roslin dependent on which node you are logged in to. In your home directory create a directory called Geant4 by [username@galactica ~] mkdir Geant4 Change to the Geant4 directory [username@galactica ~] cd Geant4 Download the folder MaS1 from Studentportalen by starting Firefox with the link [username@galactica Geant4] firefox In Firefox search for Modellering och and click on the VT 2017 entry of Modellering och simuleringsmetoder för partikeltransport

2 The MaS1 folder is found under Coursematerial 2017 Geant4 Codes, click the box in front of the MaS1 folder and press download. In the pop-up window choose Save File and press OK and close Firefox. A zip file will be created in your Downloads directory. Move the zip file to the Geant4 directory [username@galactica Geant4] mv /home/username/downloads/*.zip /home/username/geant4/. Unzip the downloaded file [username@galactica Geant4] unzip *.zip The unzip command should create a directory called MaS1 in the Geant4 directory, check with [username@galactica Geant4] ls The ls command should return the content of the Geant4 directory, in the terminal window you should see something like FilesFromCoursematerial******.zip MaS1 Check files and file structure for MaS1 Change directory to MaS1 [username@galactica Geant4] cd MaS1 Check the content of the MaS1 directory [username@galactica MaS1] ls The ls command should return build CMakeLists.txt include MaS1.cpp src MaS1.cpp is the file contacting the main function for the simulation we want to perform. Change to the build directory and do the ls command [username@galactica MaS1] cd build [username@galactica build] ls Init.mac init_vis.mac run1.mac run2.mac vis.mac Check that your build directory contains the files above. Check the files in the include directory by [username@galactica build] cd.. Move up to the above directory MaS1

3 MaS1] cd include include] ls MaSDetectorConstruction.h MaSPrimaryGeneratorAction.h MaSRunAction.h Check that your include directory contains the files above. The include directory contain user implemented header files for the C++ classes needed to create an executable. Check the files in the src directory by include] cd.. MaS1] cd src src] ls MaSDetectorConstruction.cpp MaSPrimaryGeneratorAction.cpp MaSRunAction.cpp Check that the src directory contains the files above. The src directory contains the user implemented source files for the C++ classes needed to create an executable. If all the above files are present in there correct location a make file can be created. The make file is needed to build and link an executable file. Create the make file To create the make file cd into the build directory [username@galactica src] cd /home/username/geant4/mas1/build Check that you are in the correct build directory [username@galactica build] pwd /home/username/geant4/mas1/build The pwd command should return the above string (/home/username/geant4/mas1/build) which show the current directory. Geant4 uses the CMake tool to create make files, CMake use the information provided in the file CMakeLists.txt in the MaS1 directory. To run CMake with the CMakeLists.txt as input use the following command [username@galactica build] ccmake /home/username/geant4/mas1 This will open CMake in the terminal window as shown in the figure below

4 For CMake to read the configuration file CMakeLists.txt press c and the terminal window should update to the following figure

5 Press c one more time and the press g to generate the necessary files to build and link the executable. After pressing g, CMake will terminate and you will be back to a normal terminal window. A number of files will be generated in the build directory, check that the file Makefile has been generated by [username@galactica build] ls CMakeCache.txt CMakeFiles cmake_install.cmake init.mac init_vis.mac Makefile run1.mac run2.mac vis.mac The above files and directories should exist in the build directory. Building, linking and running the simulation executable To build and link the simulation executable MaS1, in the build directory use the command make or gmake [username@galactica build] make Scanning dependencies of target MaS1 [ 20%] Building CXX object CMakeFiles/MaS1.dir/MaS1.cpp.o [ 40%] Building CXX object CMakeFiles/MaS1.dir/src/MaSDetectorConstruction.cpp.o [ 60%] Building CXX object CMakeFiles/MaS1.dir/src/MaSPrimaryGeneratorAction.cpp.o [ 80%] Building CXX object CMakeFiles/MaS1.dir/src/MaSRunAction.cpp.o /home/hjalmarsson/geant4/mas1/src/masrunaction.cpp:18:6: warning: unused parameter arun [- Wunused-parameter] void MaSRunAction::EndOfRunAction(const G4Run* arun) ^ [100%] Linking CXX executable MaS1 [100%] Built target MaS1 The above text should returned after the make command and an executable with the name MaS1 should exist in the build directory, check with ls command [username@galactica build] ls CMakeCache.txt cmake_install.cmake init_vis.mac MaS1 CMakeFiles init.mac Makefile run1.mac vis.mac run2.mac To run the executable MaS1 do [username@galactica build]./mas1 Hopefully, two new windows will be pop-up and the implemented geometry will be display in one of the windows (see below).

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7 Moreover, when running MaS1 without any arguments the input file init_vis.mac in the build directory will be used as input file to the executable, which in turn will use the information given in the file vis.mac. In the G4UIXm window in the session box write /run/beamon 10 This corresponds to a simulation of 10 gamma-rays emitted from a source located to the left of the detector volume and the result should look something like the figure below

8 To exit the geometry viewing and terminate the simulation write exit in the session box in the G4UIXm window. Useful drawing options In the G4UIXm session box some useful drawing options can be used, to add axes to the drawing write /vis/scene/add/axes m in the G4UIXm session box. To cut away a quarter of the space along the z axis write /vis/viewer/addcutawayplane m and /vis/viewer/addcutawayplane m in the G4UIXm session box. To change color of the detector logical volume in MaS1 write /vis/geometry/set/colour detectorl in the G4UIXm session box. Using the above visualization commands and some twisting and turning results in the figure below.

9 Running a simulation with an input file When the geometry, to be simulated, is implemented in the way that is required, it is advantageous to run simulations with input files. In the build directory two examples of input files are given, run1.mac and run2.mac, there the executable output, to the terminal window, is set to a minimum for run1.mac. Using run2.mac all particle interactions will be written to the terminal window. With the use of input files, changes can be made to e.g. source particle, energy of source particle and number of source particles without the need of rebuilding the source code. To run MaS1 with an input file give e.g. the following command [username@galactica build]./mas1 run1.mac If one wants to pipe the simulation outputs to a file one can do [username@galactica build]./mas1 run1.mac > run1.txt All outputs will then be piped to the file run1.txt instead of the terminal window. Also test to run MaS1 with the run2.mac input file.

10 Exercise to make a simulation geometry change, CGS solids In this exercise we should edit the simulation geometry of the MaS1 code. We should create a solid cylinder with radius 1 cm and length 5.0 cm and the corresponding logical volume with the material fworldmaterial as defined in the MaS1 code. The cylinder should be shifted 2.5 cm in the z-direction relative the already implemented rectangular detector in the MaS1 code. The edited simulation geometry should be a standalone executable with the name MaS1CGS. To do this, change to the directory Geant4 [username@galactica build] cd /home/username/geant4 Create a new directory called MaS1CGS [username@galactica Genat4] mkdir MaS1CGS Change to the created directory [username@galactica Geant4] cd MaS1CGS Copy the include and src directories from the MaS1 directory [username@galactica MaS1CGS] cp r /home/username/geant4/mas1/include. [username@galactica MaS1CGS] cp r /home/username/geant4/mas1/src. Copy the MaS1.cpp from the MaS1 directory and change the file name to MaS1CGS.cpp [username@galactica MaS1CGS] cp /home/username/geant4/mas1/mas1.cpp MaS1CGS.cpp Copy the CMakeLists.txt from the MaS1 to the MaS1CGS directory [username@galactica MaS1CGS] cp /home/username/geant4/mas1/cmakelists.txt. Open CMakeLists.txt with emacs or any text editor you like [username@galactica MaS1CGS] emacs CMakeLists.txt & In CMakeLists.txt change all instances of MaS1 to MaS1CGS Create a directory called build [username@galactica MaS1CGS] mkdir build Change to the build directory [username@galactica MaS1CGS] cd build Copy all the files ending with.mac from the MaS1/build directory [username@galactica build] cp /home/username/geant4/mas1/build/*.mac.

11 Try to build, link and run the executable MaS1CGS. If you get MaS1CGS running you can start changing the simulation geometry by editing the Construct function in the MaSDetectorConstruction.cpp file. This file should be in the directory /home/username/geant4/mas1cgs/src/. Open the file in your preferred text editor. Try to implement A new solid volume for the cylinder we want to add in the geometry using the Geant4 class G4Tubs A new logical volume to add material properties to the new cylinder using the Geant4 class G4LogicalVolume Place the logical volume using the already implemented detector volume as the mother with the use of the Geant4 class G4PVPlacement. Can you implement the same thing using Boolean solids instead for CGS solids?