Example TestEm2

How to do shower profiles in an homogenous medium, with virtual voxelisation.

GEOMETRY DEFINITION

The geometry consists of a cylinder of homogenous material.

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

Material can be choosen: Air Water lAr Al Fe BGO PbWO4 Pb. eg:

/testem/det/setMat PbWO4

The cylinder is virtually sliced longitudinally (slice) and radially (ring). The size of the slices and rings are expressed in radiation length units and can be changed. eg:

/testem/det/setLbin 20   1.    ---> 20 slices of 1. radl
/testem/det/setRbin  5   0.25  --->  5 rings of 0.25 radl
/testem/det/update             ---> rebuild the geometry

(MaxBin = 500 in both directions)

An uniform magnetic field along the cylinder axis can be set. eg:

/testem/det/setField 5 tesla 

PHYSICS LISTS

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

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

EM physics builders can be local (eg. in this example) or from G4 kernel physics_lists subdirectory.

Local physics builders:

• "local" standard EM physics with current 'best' options setting. these options are explicited in PhysListEmStandard

From geant4/source/physics_lists/builders:

• "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
• "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

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

AN EVENT : THE PRIMARY GENERATOR

The primary kinematic consists of a single particle which hits the cylinder perpendicular to the input face. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can changed via the G4 build-in commands of G4ParticleGun class (see the macros provided with this example).

A RUN is a set of events.

VISUALIZATION

The Visualization Manager is set in the main() (see TestEm2.cc). The initialisation of the drawing is done via the commands /vis/.. in the macro vis.mac. In interactive session:

PreInit or Idle > /control/execute vis.mac

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

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 one, or none. This command is defined in EventActionMessenger class.

PHYSICS DEMO

The particle's type and the physics processes which will be available in this example are set in PhysicsList class.

In addition a build-in interactive command (/process/inactivate procname) allows to activate/inactivate the processes one by one.

The threshold for producing secondaries can be changed. eg:

/testem/phys/setCuts 100 microm
/run/initialize

The shower profiles are histogramed, if histograming is activated. They can be also printed with the command /testem/run/verbose 1

HOW TO START ?

• Execute TestEm2 in 'batch' mode from macro files

  % TestEm2   run01.mac
  

• Execute TestEm2 in 'interactive mode' with visualization

  % TestEm2
  ....
  Idle> type your commands
  ....
  Idle> exit
  

Macros provided in this example:

• egs4.mac: Fe; L = 20 radl; R = 5 radl; electron 30 GeV (EGS4 simulation: Particle Data Group - Phys.Rev.D 50-3 - August94)
• run01.mac: PbWO4; L = 20 radl; R = 5 radl; electron 5 GeV
• run02.mac: Al; L = 13.5 radl; R = 1.35 radl; electron 1 GeV (Electron-induced cascade showers: J&H Crannel - Phys. Rev. 184-2 - August69)
• run03.mac: H2O; L = 9.97 radl; R = 0.665 radl; electron 1 GeV (Electron-induced cascade showers: J&H Crannel - Phys. Rev. 184-2 - August69)
• test.mac: PbWO4; L = 20 radl; R = 5 radl; electron 5 GeV
• vis.mac: to activate visualization

HISTOGRAMS

TestEm2 produces several histograms:

Content of these histo:

• 1 : energy deposit per event
• 2 : charged track length per event
• 3 : neutral track length per event
• 4 : longitudinal energy profile
• 5 : rms of longitudinal energy profile
  
• 6 : cumulated longitudinal energy profile
• 7 : rms of cumulated longitudinal energy profile
• 8 : radial energy profile
• 9 : rms of radial energy profile
  
• 10 : cumulated radial energy profile
• 11 : rms of cumulated radial energy profile

To define the output file name with histograms, use the UI command :

/analysis/setFileName name

The format of the histogram file can be : root (default), xml, csv, by selecting g4nnn.hh in RunAction.hh