GEOMETRY DEFINITION

It is a single box representing a 'semi infinite' homogeneous medium. Two parameters define the geometry:

the material of the box,
the (full) size of the box.

The default geometry (100 m of water) is constructed in DetectorConstruction, but the above parameters can be changed interactively via the commands defined in DetectorMessenger.

PHYSICS LIST

The physics list contains the standard electromagnetic processes. In order not to introduce 'articicial' constraints on the step size, there is no limitation from the maximum energy lost per step.

AN EVENT: THE PRIMARY GENERATOR

The primary kinematic consists of a single particle starting at the edge of the box. The type of the particle and its energy are set in PrimaryGeneratorAction (1 MeV electron), and can be changed via the G4 build-in commands of G4ParticleGun class (see the macros provided with this example).

PHYSICS

All discrete processes are inactivated (see provided macros), so that Multiple Scattering or Gamma Conversion is 'forced' to determine the first step of the primary particle. The step size and the final state are computed and plotted. Then the event is immediately killed.

Multiple Scattering:

The result is compared with the 'input' data, i.e. with the cross sections stored in the PhysicsTables and used by Geant4.

The stepMax command provides an additionnal control of the step size of the multiple scattering.

HISTOGRAMS

The test contains 16 built-in 1D histograms, which are managed by the HistoManager 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, etc..) (see the macros xxxx.mac).

1 : Multiple Scattering. True step length
2 : Multiple Scattering. Geom step length
3 : Multiple Scattering. Ratio geomSl/trueSl
4 : Multiple Scattering. Lateral displacement: radius
5 : Multiple Scattering. Lateral displac: psi_space
6 : Multiple Scattering. Angular distrib: theta_plane
7 : Multiple Scattering. Phi-position angle
8 : Multiple Scattering. Phi-direction angle
9 : Multiple Scattering. Correlation: cos(phiPos-phiDir)
10 : Gamma Conversion. Open Angle * Egamma
11 : Gamma Conversion. Log10(P recoil)
12 : Gamma Conversion. Phi P recoil angle
13 : Gamma Conversion. Phi P plus angle
14 : Gamma Conversion. 2 * cos(phiplus + phiminus) Asymmetry
15 : Gamma Conversion. E plus / E gamma
16 : Gamma Conversion. Phi of Gamma Polarization

The histograms are managed by the HistoManager 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 testem15)

It is possible to choose the format of the histogram file : root (default), hdf5, xml, csv, by changing the default file type in HistoManager.cc

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 testem15)

VISUALIZATION

The Visualization Manager is set in the main () (see TestEm15.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.

HOW TO START ?

Execute TestEm15 in 'batch' mode from macro files:
```
% TestEm15   compt.mac
```

Execute TestEm15 in 'interactive mode' with visualization:

% TestEm15
Idle> control/execute vis.mac
....
Idle> type your commands
....
Idle> exit

- MACROS

The examples of macros for Multiple Scattering:

electron.mac
muon.mac
proton.mac

The example of Gamma Conversion macro:

gamma.mac - gamma to e+ e-
gamma2mumu.mac gamma to mu+ mu-

Example TestEm15 - Gamma Conversion