Cosmic shower simulation in Geant4
The simulation uses CMake as buildsystem.
Dependencies are:
- Geant4 >= 10.6
- libconfig++ >= 1.7.2
To build, run cmake ../source/, then make from the build directory.
If you want to use a graphical user interface, run cmake with -DSHOWER_BUILD_UI=ON. Default is OFF.
If you want to perform benchmarks, run cmake with -DSHOWER_BENCHMARK=ON. Default is OFF.
This saves the execution time per event and measures memory usage over the program runtime. Note that this option reduces performance.
Default compiler options are
-Weverything -Wno-c++98-compat -Wno-padded -Wwrite-strings -Wpointer-arith -Woverloaded-virtual -Wall -Wextra -Wpedantic -Wshadow -Werror -O3
There are two executables generated, one is cosmic_shower, which is the simulation itself.
The other is atmosphere_layers which calculates the optimal atmosphere layer thickness.
All binaries will be placed in the build/bin/ directory.
This is the simulation software, it reads the configuration file shower.cfg from the directory it is executed from.
The simulation runs headless per default. It reads the configuration file and starts the run, while creating a data output directory as set in the configuration file by the data_directory and name preferences. In this directory all output files are placed.
These output files are:
config_dump contains the used configuration
detailed_hits contains all detailed hit information from the detectors
hits contains a list of hits on detectors with only position and timestamp to test multilateration easily
ground_intensity contains the amount of energy arrived at ground level separated into chunks
secondaries If the simulation was cut short this contains the list of all particles active in the simulation at time of shutdown
The Data in the secondaries file is formatted in the libconfig format so it can be directly used to restart the simulation with those particles
The detailed_hits file is a csv file with the follwing columns
Particle,position_x,position_y,position_z,momentum_x,momentum_y,momentum_z,momentum_magnitude,global_time,local_time,proper_time
if there are multiple runs in one simulation, each run will be separated by a # Event <n> comment.
Following commandline arguments are possible:
-h --help
Print this help
-g --graphical
Show the user interface
-o --overwrite
Overwrite existing simulation data
-c --config (value)
Use the configuration file specified in the value
The ´-g´ option is only avialable if -DSHOWER_BUILD_UI has been set to ON.
The configuration file is in the syntax of libconfig.
You can set a different config file, however the default file is always available as fallback. That means that in the individual config file you only have to set the relevant parameters and can rely on the fallback providing sane default values for the rest of the configuration.
The only required field is the name property, since that will be used as a folder name to store the resulting data from the run.
A default configuration file can be found in source/config/shower.cfg.in This file is automatically moved to the build directory by CMake. So if you need to make adjustments to the default configuation, do it in the .in file.
This program iteratively calculates the individual layer thickness according to a specific metric. The default is set to layer mass. The change is made in the line which reads
Layer* layers = Layer::create(lower, upper, new Density(), n);
There are two more targets available, one is Pressure and one is Temperature.
In case you need a different metric, inherit OptimisationTarget and pass the new child class to the create method.
The optimisation method tries to keep the integral defined by the integral method of each individual layer equal to the average of all layers.
It takes the following arguments:
-h print this help
-u <double> set upper limit unit: m
default: 40000 m
-T <double> Set temperature at sealevel unit: K
default: 288.15 K
-p <double> Set pressure at sealevel unit: Pa
default: 101325 Pa
-rho <double> Set density at sealevel unit: kg/m^3
default: 1.225 kg/m^3
-k <double> Set heat capacity ratio
default: 1.235
-n <int> set number of layers
default: 10
-csv generate csv formatted output
-config generate libconfig formatted output
The parameter -k is the heat capacit ratio. it is dependent on the temperature gradient of the atmosphere and can be calculated with the formula
κ = (M * g) / (M * g + R * dT/dh)
Due to the default temperature gradient being linear, there is a cutoff altitude which cannot be crossed. With the current default values this cutoff altitude is roughly 44300 m.