Example TestEm12

How to plot a depth dose profile in spherical geometry.

GEOMETRY DEFINITION

The geometry consists of a single sphere of an homogenous material. Optionally, the sphere can be divided in thin shells.

3 parameters define the geometry :

• the material of the sphere,
• the radius of the sphere (absorRadius),
• the number of shells (nbOfLayers)

In addition a transverse uniform magnetic field can be applied.

The default geometry is constructed in DetectorConstruction class, but all of the above parameters can be changed interactively via the commands defined in the DetectorMessenger class.

PHYSICS LIST

Physics Lists are based on modular design. Several modules are instantiated:

1. Transportation
2. EM physics
3. Decays
4. StepMax - for step limitation

The following options for EM physics using builders from physics_lists sub-package are available:

• "emstandard_opt0" recommended standard EM physics for LHC
• "emstandard_opt1" best CPU performance standard physics for LHC
• "emstandard_opt2" similar fast simulation
• "emstandard_opt3" best standard EM options - analog to "local" above
• "emstandard_opt4" best current advanced EM options standard + lowenergy
• "emstandardWVI" standard EM physics and WentzelVI multiple scattering
• "emstandardSS" standard EM physics and single scattering model
• "emstandardGS" standard EM physics and Goudsmit-Saunderson multiple scatt.
• "emlivermore" low-energy EM physics using Livermore data
• "empenelope" low-energy EM physics implementing Penelope models
• "emlowenergy" low-energy EM physics implementing experimental low-energy models
• "dna" process and models for Geant4-DNA
• "dna_opt1" process and models for Geant4-DNA
• "dna_opt2" process and models for Geant4-DNA
• "dna_opt3" process and models for Geant4-DNA
• "dna_opt4" process and models for Geant4-DNA
• "dna_opt5" process and models for Geant4-DNA
• "dna_opt6" process and models for Geant4-DNA
• "dna_opt7" process and models for Geant4-DNA

A local builder, PhysListEmStandard "local" (similar to opt0) is also available.

Physics lists and options can be (re)set with UI commands

AN EVENT : THE PRIMARY GENERATOR

The primary kinematic consists of a single particle randomly shot at the centre of the sphere. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can be changed via the G4 built-in commands of G4ParticleGun class (see the macros provided with this example).

In addition one can deactivate the randomness of the direction of the incident particle. The corresponding interactive command is built in PrimaryGeneratorMessenger class.

A RUN is a set of events.

VISUALIZATION

The Visualization Manager is set in the main () (see TestEm12.cc). The initialisation of the drawing is done via the commands /vis/... in the macro vis.mac. To get visualisation:

> /control/execute vis.mac

The detector has a default view which is a longitudinal view of the box.

The tracks are drawn at the end of event, and erased at the end of run. Optionally one can choose to draw all particles, only the charged ones, or none. This command is defined in EventActionMessenger class.

HOW TO START ?

• Execute TestEm12 in 'batch' mode from macro files

  % TestEm12   run01.mac
  

• Execute TestEm12 in 'interactive mode' with visualization

  % TestEm12
  ....
  Idle> type your commands
  ....
  Idle> exit
  

Macros provided in this example:

• berger.mac: e- (100 keV) on water
• dna.mac: e- (1 keV) on water. DNA physics list
• run01.mac: e- (4 MeV) on water. Step max from histos 1 and 8
• run02.mac: e- (4 MeV) on water. Step max from geometry

Macros to be run interactively:

• vis.mac: To activate visualization

TRACKING and STEP MAX

TestDm12 computes the total energy deposited along the trajectory of the incident particle : the so-called longitudinal energy profile, or depth dose distribution. The energy deposited (edep) is randomly distributed along the step (see SteppingAction).

In order to control the accuracy of the deposition, the maximum step size of charged particles is computed automatically from the binning of histograms 1 and 8 (see RunAction).

As an example, this limitation is implemented as a 'full' process : see StepMax class and its messenger. The 'StepMax process' is registered in the Physics List.

StepMax is evaluated in RunAction::BeginOfRun() and passed to the StepMax process. A boolean UI command allows to deactivate this mechanism. Another UI command allows to define directly a stepMax value.

HISTOGRAMS

Testem12 has several predefined 1D histograms :

• 1 : energy profile dE/dr (in MeV/mm per event)
• 2 : total energy deposited in the absorber
• 3 : total track length of the primary track
• 4 : step size of the primary track
  
• 5 : projected range of the primary track
• 6 : total track length of charged secondary tracks
• 7 : step size of charged secondary tracks
  
• 8 : normalized energy profile d(E/E0)/d(r/r0), where r0 is the range of the primary particle of energy E0

The histograms are managed by G4AnalysisManager class and its messenger. The histos can be individually activated with the command :

/analysis/h1/set id nbBins  valMin valMax unit 

where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)

One can control the name of the histograms file with the command:

/analysis/setFileName  name  (default testem12)

It is possible to choose the format of the histogram file : root (default), xml, csv, by using namespace in HistoManager.hh

It is also possible to print selected histograms on an ascii file:

/analysis/h1/setAscii id

All selected histos will be written on a file name.ascii (default testem12)