Example for investigation of ionisation in thin absorbers and gaseous detectors

GEOMETRY DEFINITION

The target is a cylinder made of a given material placed inside cylindrical container, which is placed inside the world volume.

Following parameters define the geometry:

the material of the target,
the thickness of the target,
the radius of the target,
the material of the container,
the thickness of the container,
the material of the world.

The list of materials used in gaseous detectors are built inside the DetectorConstruction class, also NIST materials are available. The default geometry is provided but all parameters can be changed via UI commands defined in the DetectorMessenger class, for example,

/testem/setGasMat      XeCH4C3H8
/testem/setWindowMat   G4_MYLAR
/testem/setWorldMat    G4_AIR
/testem/setGasThick    10 cm
/testem/setGasRad      20 cm
/testem/setWindowThick 50 um

AN EVENT : THE PRIMARY GENERATOR

The primary kinematic consists of a single particle which hits the absorber perpendicular to the input face. The type of the particle and its energy can be set via the G4 build-in commands of G4ParticleGun . A RUN is a set of events.

DETECTOR RESPONSE

The TargetSD class sending information about each step inside the target to the HistoManager class scoring of energy deposition in the detector. Additionally at each step of a particle inside the target the number of ionisation clusters is sampled using G4ElectronIonPair helper class. The parameter of transformation of energy into ionisation clusters can be set via UI command:

/testem/setPairEnergy 19 eV

PHYSICS

The particle's type and the physics processes which will be available in this example are set in PhysicsList class, which uses Geant4 EM physics constructors provided in the physics_list library.

The PhysicsListMessenger classes introduce interactive commands. In particular, PAI ionisation model can be added using G4EmConfigurator helper class, which is invoked by the UI command

/testem/phys/addPhysics pai

HOW TO START ?

Execute TestEm8 in 'batch' mode from macro files e.g.
```
% $(G4INSTALL)/bin/$(G4SYSTEM)/TestEm8  TestEm8.in N
```
here N means number of threads in multi-threaded mode, by default 2 threads are used

Execute TestEm8 in 'interactive' mode with visualization e.g.

% $(G4INSTALL)/bin/$(G4SYSTEM)/TestEm8
....
Idle> type your commands
....