Gabriele Cosmo
130 lines
4.8 KiB
Plaintext
130 lines
4.8 KiB
Plaintext
$Id: README,v 1.9 2010-04-02 13:22:02 maire Exp $
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-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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Hadr03
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------
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How to compute total cross section from the direct evaluation of the
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mean free path ( see below, item Physics).
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How to identify nuclear reactions.
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How to plot energy spectrum of secondary particles.
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1- GEOMETRY DEFINITION
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It is a single box representing a 'semi infinite' homogeneous medium.
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Two parameters define the geometry :
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- the material of the box,
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- the (full) size of the box.
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The default geometry (10 m of molybdenum) is built in DetectorConstruction,
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but the above parameters can be changed interactively via commands defined
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in DetectorMessenger.
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2- PHYSICS LIST
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The PhysicsList contains builders for hadronic interactions.
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Predefined G4 PhysicsConstructors or 'local' PhysicsConstructors can be used
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(see geant4/source/physics_lists or example runAndEvent/RE04).
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In order not to introduce 'artificial' constraints on the step size,
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electromagnetic processes are not registered: there is no continuous energy
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loss.
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting at the edge
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of the box. The type of the particle and its energy are set in
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PrimaryGeneratorAction (neutron 1 MeV), and can be changed via the G4
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build-in commands of ParticleGun class (see the macros provided with
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this example).
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4- PHYSICS
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An event is killed at the first interaction of the incident paticle.
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The absorption length, also called mean free path, is computed as
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the mean value of the track length of the incident particle.
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This is why the medium must be 'infinite' : to be sure that interaction
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occurs at any events.
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The result is compared with the 'input' value, i.e. with the cross sections
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given by G4HadronicProcessStore and used by Geant4.
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The list of nuclear reactions that occured is printed.
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(the number of gamma of deexcitation is not printed).
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Then, comes the total list of generated particles and ions.
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The energy spectrum of the scattered particle (if any) and of the created
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secondaries are plotted (see SteppingAction).
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Momentum conservation is checked as :
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momentum balance = modulus(P_out - P_in)
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A set of macros defining various run conditions are provided.
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The processes can be actived/inactived in order to survey the processes
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individually.
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5- HISTOGRAMS
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The test contains 12 built-in 1D histograms, which are managed by
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G4AnalysisManager and its Messenger. The histos can be individually
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activated with the command :
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/analysis/h1/set id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, etc..)
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(see the macros xxxx.mac).
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1 "kinetic energy of scattered primary particle"
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2 "kinetic energy of recoil nuclei"
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3 "kinetic energy of gamma"
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4 "kinetic energy of neutrons"
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5 "kinetic energy of protons"
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6 "kinetic energy of deuterons"
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7 "kinetic energy of alphas"
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8 "kinetic energy of all others ions"
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9 "kinetic energy of all others mesons"
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10 "kinetic energy of all others baryons"
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11 "Q = Ekin out - Ekin in"
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12 "Pbalance = mag(P_out - P_in)"
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The histograms are managed by the HistoManager class and its Messenger.
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The histos can be individually activated with the command :
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/analysis/h1/set id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default Hadr03)
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It is possible to choose the format of the histogram file : root (default),
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xml, csv, by using namespace in HistoManager.hh
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It is also possible to print selected histograms on an ascii file:
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/analysis/h1/setAscii id
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All selected histos will be written on a file name.ascii (default Hadr03)
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6- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via the commands
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/vis/... in the macro vis.mac. To get visualisation:
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> /control/execute vis.mac
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The detector has a default view which is a longitudinal view of the box.
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The tracks are drawn at the end of event, and erased at the end of run.
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7- HOW TO START ?
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Execute Hadr03 in 'batch' mode from macro files :
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% Hadr03 inelastic.mac
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Execute Hadr03 in 'interactive mode' with visualization :
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% Hadr03
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Idle> control/execute vis.mac
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....
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Idle> type your commands
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....
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Idle> exit
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