geant4

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

(MaxBin = 500 in both directions)

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

/globalField/setValue 0 0 5 tesla

PHYSICS LISTS

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

Transportation
EM physics
Decays
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(). 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 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 'batch' mode using multi-threading

% ./TestEm2   run01.mac 4

 here 4 is number of threads, it should be user defined,
 optimal value depends on hardware

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
stepMax.mac: chargedgeantino in PbWO4; To illustrate step max mechanism;
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 changing the default file type in RunAction.cc.