Gabriele Cosmo
161 lines
6.7 KiB
Plaintext
161 lines
6.7 KiB
Plaintext
|
||
=========================================================
|
||
Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
||
=========================================================
|
||
|
||
Activation
|
||
----------
|
||
|
||
Survey energy deposition and particle's flux from an hadronic cascade,
|
||
including radioactive decays.
|
||
The main purpose of the example is to plot evolution of each metastable isomer
|
||
as a function of time, taking into account the time of exposure in the beam.
|
||
Also plot the activity of emerging particles.
|
||
Use PhysicsConstructor objects rather than predefined G4 PhysicsLists.
|
||
|
||
1- MATERIALS AND GEOMETRY DEFINITION
|
||
|
||
The "absorber" is a box made of a given material.
|
||
|
||
Three parameters define the absorber :
|
||
- the material of the absorber
|
||
- the thickness of an absorber
|
||
- the transverse size of the absorber (the input face is a square)
|
||
|
||
The volume "World" contains the "absorber".
|
||
|
||
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 DetectorConstruction::DefineMaterials().
|
||
|
||
2- PHYSICS LIST
|
||
|
||
The physics list contains a "full" set of physics processes. It is defined in
|
||
the PhysicsList class as a Geant4 modular physics list with registered physics
|
||
constructors (builders).
|
||
|
||
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.
|
||
In particular, no step constraint is imposed for energy loss mechanism (ionisation and brems).
|
||
This is enough when spatial distribution of deposited energy do not need
|
||
to be accurate (see param->SetStepFunction(1., 1*mm)).
|
||
|
||
Several hadronic physics options are controlled by environment variables.
|
||
To trigger them, the envHadronic.csh script has been added in this example.
|
||
One must select the options wished, and do
|
||
source envHadronic.[c]sh
|
||
|
||
3- AN EVENT : THE PRIMARY GENERATOR
|
||
|
||
The primary kinematic is a single particle which hits the absorber
|
||
perpendicular to the input face. The type of 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).
|
||
|
||
One can control the transverse size of the beam.
|
||
The command /testhadr/gun/beamSize is built in PrimaryGeneratorMessenger class.
|
||
|
||
The time of exposure in the beam may be finite. It is controled by the command
|
||
/testhadr/gun/beamTime.
|
||
Then the time zero of each event is randomly chosen within this interval.
|
||
|
||
4- PHYSICS
|
||
|
||
The program computes and plots energy deposited in the interaction volume
|
||
(absorber), energy spectrum and activity of particles leaving the absorber,
|
||
and evolution of population of metastable isomers within the absorber
|
||
(see below : histograms).
|
||
Processes invoked and particles generated during interactions are listed.
|
||
|
||
5- HISTOGRAMS
|
||
|
||
The test contains 43 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 deposit"
|
||
2 "Edep (MeV/mm) profile along beam direction"
|
||
3 "total kinetic energy emerging"
|
||
4 "energy spectrum of emerging gamma"
|
||
5 "energy spectrum of emerging e+-"
|
||
6 "energy spectrum of emerging neutrons"
|
||
7 "energy spectrum of emerging protons"
|
||
8 "energy spectrum of emerging deuterons"
|
||
9 "energy spectrum of emerging alphas"
|
||
10 "energy spectrum of all others emerging ions"
|
||
11 "energy spectrum of all others emerging baryons"
|
||
12 "energy spectrum of all others emerging mesons"
|
||
13 "energy spectrum of all others emerging leptons (neutrinos)"
|
||
14 "dN/dt (becquerel) of emerging gamma"
|
||
15 "dN/dt (becquerel) of emerging e+-"
|
||
16 "dN/dt (becquerel) of emerging neutrons"
|
||
17 "dN/dt (becquerel) of emerging protons"
|
||
18 "dN/dt (becquerel) of emerging deuterons"
|
||
19 "dN/dt (becquerel) of emerging alphas"
|
||
20 "dN/dt (becquerel) of all others emerging ions"
|
||
21 "dN/dt (becquerel) of all others emerging baryons"
|
||
22 "dN/dt (becquerel) of all others emerging mesons"
|
||
23 "dN/dt (becquerel) of all others emerging leptons (neutrinos)"
|
||
|
||
Histograms 24 to 43 are assigned to population of metastable isomer.
|
||
Here, ´metastable' means time life > 0.
|
||
|
||
The type and number of isomers created in a run cannot be predicted in advance.
|
||
Therefore the assignation : isomer <--> histo_Id is done on fly
|
||
and printed at end of run. A lock mechanism is necessary in MT mode; see Run.cc
|
||
|
||
Activation and binning control of histograms is done with the usual command
|
||
/analysis/h1/set
|
||
|
||
One can control the name of the histograms file with the command:
|
||
/analysis/setFileName name (default Activation)
|
||
|
||
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 Activation)
|
||
|
||
6- 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
|
||
|
||
7- HOW TO START ?
|
||
|
||
Execute Activation in 'batch' mode from macro files :
|
||
% ./Activation run1.mac
|
||
|
||
Execute Activation in 'interactive mode' with visualization :
|
||
% ./Activation
|
||
Idle> control/execute vis.mac
|
||
....
|
||
Idle> type your commands
|
||
....
|
||
Idle> exit
|