$Id: README 107435 2017-11-13 07:34:58Z gcosmo $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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TestEm5
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How to study the transmission, absorption and reflection of particles through
a single, thin or thick, layer of material.
In particular, the effects of the multiple scattering can be plotted.
1- 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).
A volume "World" contains the "absorber".
In addition a transverse uniform magnetic field can be applied.
The default geometry is constructed in DetectorConstruction class, but all the
parameters can be changed via commands defined in the DetectorMessenger class.
The parameters of the "World" can be changed, too. However, if World material
is not set to vacuum, the plots 10->43 below may be not pertinent.
2- PHYSICS LIST
Physics lists are based on modular design. Several modules are instantiated:
1. Transportation
2. EM physics
3. Decays
4. StepMax - for step limitation
EM physics builders can be local (eg. in this example) or from G4 kernel
physics_lists subdirectory.
Local physics builders:
- "local" standard EM physics with current 'best' options setting
these options are explicited in PhysListEmStandard
- "standardSSM" standard EM physics with alternative single Coulomb
scattering model instead of multiple scattering.
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
- "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
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.
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle which hits the absorber
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 interactive command is built in PrimaryGeneratorMessenger class.
4- VISUALIZATION
The Visualization Manager is set in the main().
The initialisation of the drawing is done via the commands in vis.mac
In interactive session:
PreInit or Idle > /control/execute vis.mac
The example has a default view which is a longitudinal view of the detector.
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, or none.
This command is defined in EventActionMessenger class.
5- TRACKING
During the tracking, one can keep or not the secondaries : see StackingAction
class and its Messenger (StackingMessenger).
One can also limit 'by hand' the step lenght of the particle. 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.
6- DETECTOR RESPONSE
At the end of a run, from the histogram(s), one can study different
physics quantities such as :
- energy deposit in the absorber,
- energy spectrum of secondaries at creation,
- energy spectrum and angle distribution of particles at exit,
- transmission and backscattering coefficients,
- ...
7- List of the built-in histograms
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The test contains more than 60 built-in 1D histograms, which are managed by
G4AnalysisManager 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..)
(see the macros xxxx.mac).
1 "energy deposit in absorber"
2 "energy of charged secondaries at creation"
3 "energy of neutral secondaries at creation"
4 "energy of charged at creation (log10(Ekin))"
5 "energy of neutral at creation (log10(Ekin))"
6 "x_vertex of charged secondaries (all)"
7 "x_vertex of charged secondaries (not absorbed)"
10 "(transmit, charged) : kinetic energy at exit of world"
11 "(transmit, charged) : ener fluence: dE(MeV)/dOmega"
12 "(transmit, charged) : space angle dN/dOmega"
13 "(transmit, charged) : projected angle at exit of world"
14 "(transmit, charged) : projected position at exit of world"
15 "(transmit, charged) : radius at exit of world"
20 "(transmit, neutral) : kinetic energy at exit of world"
21 "(transmit, neutral) : ener fluence: dE(MeV)/dOmega"
22 "(transmit, neutral) : space angle dN/dOmega"
23 "(transmit, neutral) : projected angle at exit of world"
30 "(reflect , charged) : kinetic energy at exit of world"
31 "(reflect , charged) : ener fluence: dE(MeV)/dOmega"
32 "(reflect , charged) : space angle dN/dOmega"
33 "(reflect , charged) : projected angle at exit of world"
40 "(reflect , neutral) : kinetic energy at exit of world"
41 "(reflect , neutral) : ener fluence: dE(MeV)/dOmega"
42 "(reflect , neutral) : space angle dN/dOmega"
43 "(reflect , neutral) : projected angle at exit of world"
50 "energy of Auger e- at creation"
51 "energy of fluorescence gamma at creation"
52 "energy of Auger e- at creation (log scale)"
53 "energy of fluorescence gamma at creation (log scale)"
54 "energy of PIXE Auger e- at creation"
55 "energy of PIXE gamma at creation"
56 "energy of PIXE Auger e- at creation (log scale)"
57 "energy of PIXE gamma at creation (log scale)"
58 "energy of G4DNA Auger e- at creation"
59 "energy of G4DNA gamma at creation"
60 "energy of G4DNA Auger e- at creation (log scale)"
61 "energy of G4DNA gamma at creation (log scale)"
The histograms can be viewed using ROOT or PAW.
One can control the name of the histograms file with the command:
/analysis/setFileName name (default testem5)
It is possible to choose the format of the histogram file : root (default),
hbook, 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 testem5)
8- GEANT4/GEANT3/DATA COMPARISON
A Geant4/Geant3/exp. data comparison is given here for a few cases.
These cases can be classified as follow:
- e-/e+ incident particles versus protons and others.
- 3 energy regimes: low: < 1MeV; medium: 1MeV -> few 10MeV; high: > 100MeV
We indicate here the corresponding macros.
| low energy | medium energy | high energy
--------------------------------------------------------
| acosta.mac | |
e-+ | berger.mac | hanson.mac |
| hunger.mac | kulchi.mac |
| tavola.mac | |
--------------------------------------------------------
others| bichsel.mac | vincour.mac | shen1.mac shen2.mac
| | gottsch.mac | tramu.mac
--------------------------------------------------------
The relevant part of the GEANT3 code is in the subdirectory geant3 together
with the xxxx.dat input files.
9- HOW TO START ?
- execute TestEm5 in 'batch' mode from macro files e.g.
% $(G4INSTALL)/bin/$(G4SYSTEM)/TestEm5 myMacro.mac
- execute TestEm5 in 'interactive' mode with visualization e.g.
% $(G4INSTALL)/bin/$(G4SYSTEM)/TestEm5
Then type your commands, for instance :
Idle> control/execute vis.mac
Idle> run/beamOn 5
....
Gabriele Cosmo