Survey energy deposition and particle's flux from an hadronic cascade. Use PhysicsConstructor objects rather than predefined G4 PhysicsLists. How to plot a depth dose profile in a rectangular box.

MATERIALS AND GEOMETRY DEFINITION

The geometry consists of a stack of one or several blocks of homogenous material, called absorbers.

A minimum of 4 parameters define the geometry :

the number of absorbers (NbOfAbsor)
the material of each absorber,
the thickness of each absorber,
the tranverse dimension of the stack (sizeYZ)

In addition a transverse uniform magnetic field can be applied. eg: /globalField/setValue 0 0 5 tesla

The absorber is surrounded by a World volume (vacuum)

A function, and its associated UI command, allows to build a material directly from a single isotope.

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

To be identified by the ThermalScattering module, the elements composing a material must have a specific name (see G4ParticleHPThermalScatteringNames.cc) Examples of such materials are build in Hadr06/src/DetectorConstruction.

PHYSICS LIST

"Full" set of physics processes are registered, but via PhysicsConstructor objects rather than complete pre-defined G4 physics lists. This alternative way gives more freedom to register physics.

Physics constructors are either constructors provided in Geant4 (with G4 prefix) or 'local'. They include : HadronElastic, HadronInelastic, IonsInelastic, GammaNuclear, RadioactiveDecay and Electomagnetic. (see geant4/source/physics_lists/constructors)

HadronElasticPhysicsHP include a model for thermalized neutrons, under the control of a command defined in NeutronHPMesseger.

GammmaNuclearPhysics is a subset of G4BertiniElectroNuclearBuilder.

ElectromagneticPhysics is a simplified version of G4EmStandardPhysics.

Several hadronic physics options are controlled by environment variables. To select them, see Hadr07.cc

AN EVENT : THE PRIMARY GENERATOR

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

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

A RUN is a set of events.

PHYSICS

The program computes the energy deposited in each absorber, and the flux of particles emerging in the world. Processes invoked and particles generated are listed.

HISTOGRAMS

The test has several built-in 1D histograms, which are managed by G4AnalysisManager 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     "total energy deposited in absorber 1
      2     "total energy deposited in absorber 2
      ...........................................
      9     "total energy deposited in absorber 9
      10    "Edep (MeV/mm) profile along absorbers"
      11    "total Energy deposited in all absorbers"
      12    "total Energy leakage"
      13    "total Energy released"

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

  /analysis/setFileName  name  (default Hadr07)

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 Hadr07)

TRACKING and STEP MAX

Hadr07 computes the distribution of energy deposited along the trajectory of the incident particle : the so-called longitudinal energy profile, or depth dose distribution (histogram 10). The energy deposited (edep) is randomly distribued 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 histogram 10.

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, via a physicsConstructor object (a builder).

StepMax is evaluated in the StepMax process. A boolean UI command allows to deactivate this mechanism. Another UI command allows to define directly a stepMax value.

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. To get visualisation:

   > /control/execute vis.mac

The tracks are drawn at the end of event, and erased at the end of run.
gamma green
neutron yellow negative particles (e-, ...) red positive particles (e+, ions, ...) blue

HOW TO START ?

Execute Hadr07 in 'batch' mode from macro files :

        % Hadr07   neutron.mac

Execute Hadr07 in 'interactive mode' with visualization :

        % Hadr07
        Idle> control/execute vis.mac
        ....
        Idle> type your commands
        ....
        Idle> exit

Macros provided in this example:

neutron.mac: neutron (14.1 MeV) in 30 cm of Li7
Na22.mac: multilayers. Radioactive source
alpha.mac: alpha (400 MeV). Limit the step size from histo 10
ionC12.mac: C12 (2.4 GeV). Limit the step size from histo 10
water.mac: e- (4 MeV) in Water

Macros to be run interactively:

proton.mac: proton (1 GeV). Multilayers
vis.mac: To activate visualization