How to produce a Bragg curve in a water phantom.
How to compute the dose in 'test volumes' called tallies.
How to define a maximum step size.

GEOMETRY DEFINITION

The geometry consists of a single block of a homogenous material, placed in a world.

Three parameters define the geometry :

the material of the box,
the thickness of the box (sizeX),
the transverse dimension of the box (sizeYZ).

The default is 20 cm of water.

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.

The size, matter, positions of several test-volumes (tallies) can be defined via UI commands : /testem/det/tally...

PHYSICS LIST

Physics lists can be local (eg. in this example) or from G4 kernel physics_lists subdirectory.

Local physics lists:

"local" standard EM physics with current 'best' options setting. these options are explicited in PhysListEmStandard
"standardSS" standard EM physics with single Coulomb scattering instead of multiple scattering;
"standardNR" standard EM physics with single Coulomb scattering process G4ScreenedNuclearRecoil instead of the multiple scattering for ions with energy less than 100 MeV/nucleon; the new process was developed by M.H. Mendenhall and R.A. Weller from Vanderbuilt University and published in NIM B 277 (2005) 420. In later Geant4 releases the process will be a part of Geant4 source, currently it is released together with its mathematical tool c2_functions in current

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
"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

Decay and StepMax processes are added to each list.

Optional components can be added:

"elastic" elastic scattering of hadrons
"HElastic"
"QElastic"
"binary" QBBC configuration of hadron inelastic models
"binary_ion" Binary ion inelastic models
"ionIoni" Ion gas models

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

Please, notice that options set through G4EmProcessOptions are global, eg for all particle types. In G4 builders, it is shown how to set options per particle type.

AN EVENT : THE PRIMARY GENERATOR

The primary kinematic consists of a single particle which hits the block 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). The default is a 160 MeV proton.

In addition one can define randomly the impact point of the incident particle. The corresponding interactive command is built in PrimaryGeneratorMessenger class.

A RUN is a set of events.

DOSE IN 'TEST-VOLUMES'

The energy deposited in the test-volumes (tallies) defined in DetectorConstruction are printed at RunAction::EndOfRunAction(), both in MeV and gray.

VISUALIZATION

The Visualization Manager is set in the main () (see TestEm7.cc). The initialisation of the drawing is done via the command

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

HOW TO START ?

Execute Test in 'batch' mode from macro files
```
% TestEm7    proton.mac
```

Execute Test in 'interactive mode' with visualization

% TestEm7 
        ....
Idle> type your commands
        ....
Idle> exit

HISTOGRAM OF THE BRAGG PEAK

Testem7 computes the total energy deposited along the trajectory of the incident particle : the so-called Bragg peak.

In order to control the accuracy of the deposition, the user can limit the maximum allowed for the step size of charged particles. (command /testem/stepMax )

The result is a 1D histogram, which is the total energy deposited along the trajectory of the incident particle.

The bin size is equal to stepMax. The number of bins is determined by the thickness of the absorber (with a minimum of 100 bins). The total energy deposited is plotted in MeV/mm per incident particle.

The next histogram allows to have a zoom around the Bragg peak. Its binning should be defined via UI command:

/analysis/h1/set 2 nbins xmin xmax unit

The last histogram shows the projectile range. Its bining should be defined similary by the UI command:

/analysis/h1/set 3 nbins xmin xmax unit

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

/analysis/setFileName  name  (default testem7)

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 testem7)