Author: A.Bagulya, I.Gudowska, V.Ivanchenko, N.Starkov
CERN, Geneva, Switzerland
Karolinska Institute & Hospital, Stockholm, Sweden
Lebedev Physical Institute, Moscow, Russia

This example application is based on the application IION developed for simulation of proton or ion beam interaction with a water target. Different aspects of beam target interaction are demonstrating in the example including longitudinal profile of energy deposition, spectra of secondary particles, spectra of particles leaving the target. The results are presenting in a form of average numbers and histograms.

GEOMETRY

The Target volume is a cylinder placed inside Check cylindrical volume. The Check volume is placed inside the World volume. The radius and the length of the Check volume are 1 mm larger than the radius and the length of the Target. The material of the Check volume is the same as the World material. The World volume has the sizes 10 mm larger than that of the Target volume. Any material from the Geant4 database can be defined. The default World material is G4Galactic and the default Target material is aluminum. The Target is subdivided on number of equal slices. Following UI commands are available to modify the geometry:

/testhadr/TargetMat     G4_Pb
/testhadr/WorldMat      G4_AIR
/testhadr/TargetRadius  10 mm
/testhadr/TargetLength  20 cm
/testhadr/NumberDivZ    200

Beam direction coincides with the target axis and is Z axis in the global coordinate system. The beam starts 5 mm in front of the target. G4ParticleGun is used as a primary generator. The energy and the type of the beam can be defined via standard UI commands

/gun/energy   15 GeV
/gun/particle proton

Default beam position is -(targetHalfLength + 5*mm) and direction along Z axis. Beam position and direction can be changed by gun UI commands:

/gun/position  1 10 3 mm
/gun/direction 1 0 0

however, position command is active only if before it the flag is set

/testhadr/DefaultBeamPosition false

SCORING

The scoring is performed with the help of UserStackingAction class and two sensitive detector classes: one associated with a target slice, another with the Check volume. Each secondary particle is scored by the StackingAction. In the StackingAction it is also possible to kill all or one type of secondary particles

/testhadr/Kill             neutron
/testhadr/KillAllSecondaries

To control running the following options are available:

/testhadr/PrintModulo      100
/testhadr/DebugEvent       977

The last command selects an events, for which "/tracking/verbose 2" level of printout is established.

PHYSICS

PhysicsList of the application uses reference Phsyics Lists or its components, which are distributed with Geant4 in /geant4/physics_lists subdirectory.

The reference Physics List name may be defined in the 3d argument of the run command:

Hadr01 my.macro QGSP_BERT

If 3d argument is not set then the PHYSLIST environment variable is checked. If 3d argument is set, it is possible to add the 4th and 5th arguments, which defines overlap energies between cascade and string models in GeV:

Hadr01 my.macro QGSP_BERT 3.5 8.0

If 6 arguments are used the last enabling addition of charge exchange physics on top of any reference Physics List.

Hadr01 my.macro QGSP_BERT 3.5 8.0 CI

If both 3d argument and the environment variable are not defined then reference Phsyics Lists is not instantiated, instead the local Physics List is used built from components, which may be configured using UI interface. The choice of the physics is provided by the UI command:

/testhadr/Physics     QGSP_BIC

To see the list of available configurations with UI one can use

/testhadr/ListPhysics

The cuts for electromagnetic physics can be established via

/testhadr/CutsAll       1 mm
/testhadr/CutsGamma   0.1 mm
/testhadr/CutsEl      0.2 mm
/testhadr/CutsPos     0.3 mm
/testhadr/CutsProt    0.6 mm

Note that testhadr UI commands are not available in the case when PHYSLIST environment variable is defined.

VISUALIZATION

For interactive mode G4 visualization options and variables should be defined, then the example should be recompiled:

gmake visclean
gmake

HISTOGRAMS

There are built in histograms. The 1st one (idx=0, id="1") scores energy deposition along the target. Histograms "22", "23", "24", "25" scores energy deposition per particle type.

All other histograms are provided in decimal logarithmic scale (log10(E/MeV), where E is secondary particle energy at production

It is possible to change scale and output file name using UI commands:

/testhadr/histo/fileName name
/testhadr/histo/setHisto idx nbins vmin vmax unit

Only ROOT histograms are available.

All histograms are normalized to the number of events.