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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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Hadr05
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How to collect energy deposition in a sampling calorimeter.
How to survey energy flow.
Hadr05 is the hadronic equivalent of TestEm3.
1- GEOMETRY DEFINITION
The calorimeter is a box made of a given number of layers.
A layer consists of a sequence of various absorbers (maximum MaxAbsor=9).
The layer is replicated.
Parameters defining the calorimeter :
- the number of layers,
- the number of absorbers within a layer,
- the material of the absorbers,
- the thickness of the absorbers,
- the transverse size of the calorimeter (the input face is a square).
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 modified interactively via the commands
defined in the DetectorMessenger class.
|<----layer 0---------->|<----layer 1---------->|<----layer 2---------->|
| | | | |
==========================================================================
|| | || | || | ||
|| | || | || | ||
|| abs 1 | abs 2 || abs 1 | abs 2 || abs 1 | abs 2 ||
|| | || | || | ||
|| | || | || | ||
beam || | || | || | ||
======> || | || | || | ||
|| | || | || | ||
|| | || | || | ||
|| | || | || | ||
|| | || | || | ||
|| cell 1 | cell 2 || cell 3 | cell 4 || cell 5 | cell 6 ||
==========================================================================
^ ^ ^ ^ ^ ^ ^
pln1 pln2 pln3 pln4 pln5 pln6 pln7
NB. The number of absorbers and the number of layers can be set to 1.
In this case we have a unique homogeneous block of matter, which looks like
a bubble chamber rather than a calorimeter ...
(see the macro emtutor.mac)
A function, and its associated UI command, allows to build a material
directly from a single isotope.
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.cc
2- PHYSICS LISTS
"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 the command /testhadr/phys/thermalScattering
GammmaNuclearPhysics is a subset of G4BertiniElectroNuclearBuilder.
ElectromagneticPhysics is a readable version of G4EmStandardPhysics_opt3.
Several hadronic physics options are controlled by environment variables.
To select them, see Hadr07.cc
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle which hits the calorimeter
perpendicular to the input face. 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 PrimaryGeneratorAction.
A RUN is a set of events.
Hadr05 computes the energy deposited per absorber and the energy flow through
the calorimeter.
4- VISUALIZATION
The Visualization Manager is set in the main() (see Hadr05.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 default view is a longitudinal view of the calorimeter.
5- 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 built-in interactive command (/process/inactivate processName)
allows to activate/inactivate the processes one by one.
Then one can well visualize the processes one by one, especially
in the bubble chamber setup with a transverse magnetic field.
6- HOW TO START ?
- Execute Hadr05 in 'batch' mode from macro files
% Hadr05 Cu-lAr.mac
- Execute Hadr05 in 'interactive mode' with visualization
% Hadr05
....
Idle> type your commands. For instance:
Idle> /control/execute vis.mac
....
Idle> exit
Macros provided in this example:
- Fe-Sci.mac, Cu-lAr.mac, Pb-lAr.mac, W-lAr.mac : names are self explanatory
- emtest.mac, emtutor.mac : to be run interactively
- vis.mac: to activate visualization
7- HISTOGRAMS
Hadr05 can produce histograms :
histo 1 : energy deposit in absorber 1
histo 2 : energy deposit in absorber 2
...etc...........
histo 11 : longitudinal profile of energy deposit in absorber 1 (MeV/event)
histo 12 : longitudinal profile of energy deposit in absorber 2 (MeV/event)
...etc...........
histo 21 : energy flow (MeV/event)
histo 22 : total energy deposited
histo 23 : total energy leakage
histo 24 : total energy released : Edep + Eleak
NB. Numbering scheme for histograms:
layer : from 1 to NbOfLayers (included)
absorbers : from 1 to NbOfAbsor (included)
planes : from 1 to NbOfLayers*NbOfAbsor + 1 (included)
One can control the binning of the histo with the command:
/analysis/h1/set idAbsor nbin Emin Emax unit
where unit is the desired energy unit for that histo
One can control the name of the histograms file with the command:
/analysis/setFileName name (default hadr05)
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 hadr05)
Gabriele Cosmo