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0001 -------------------------------------------------------------------
0002
0003 =========================================================
0004 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
0005 =========================================================
0006
0007 TestEm14
0008 --------
0009
0010 How to compute cross sections from the direct evaluation of the mean
0011 free path ( see below, item Physics).
0012 How to plot final state of a process.
0013
0014 1- GEOMETRY DEFINITION
0015
0016 It is a single box representing a 'semi infinite' homogeneous medium.
0017 Two parameters define the geometry :
0018 - the material of the box,
0019 - the (full) size of the box.
0020
0021 The default geometry (100 m of water) is constructed in
0022 DetectorConstruction, but the above parameters can be changed
0023 interactively via the commands defined in DetectorMessenger.
0024
0025 2- PHYSICS LIST
0026
0027 The physics list contains the standard electromagnetic processes.
0028 In order not to introduce 'artificial' constraints on the step size, the
0029 multiple scattering is not instanciated, and all processes are
0030 registered as discrete : there is no continuous energy loss.
0031
0032 3- AN EVENT : THE PRIMARY GENERATOR
0033
0034 The primary kinematic consists of a single particle starting at the edge
0035 of the box. The type of the particle and its energy are set in
0036 PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
0037 build-in commands of ParticleGun class (see the macros provided with
0038 this example).
0039
0040 4- PHYSICS
0041
0042 An event is killed at the first interaction of the incident paticle.
0043 The absorption length, also called mean free path, is computed as
0044 the mean value of the track length of the incident particle.
0045 This is why the medium must be 'infinite' : to be sure that interaction
0046 occurs at any events.
0047
0048 The result is compared with the 'input' data, i.e. with the cross
0049 sections stored in the PhysicsTables and used by Geant4.
0050
0051 The energy spectrum and the angular distribution of the scattered
0052 particle (if any) and of the created secondaries are plotted (see
0053 SteppingAction).
0054
0055 A set of macros defining various run conditions are provided.
0056 The processes are actived/inactived in order to survey the processes
0057 individually.
0058
0059 5- HISTOGRAMS
0060
0061 The test contains 6 built-in 1D histograms, which are managed by the
0062 HistoManager class and its Messenger. The histos can be individually
0063 activated with the command :
0064 /analysis/h1/set id nbBins valMin valMax unit
0065 where unit is the desired unit for the histo (MeV or keV, etc..)
0066 (see the macros xxxx.mac).
0067
0068 1 "scattered primary particle: energy spectrum"
0069 2 "scattered primary particle: costheta distribution"
0070 3 "charged secondaries: energy spectrum"
0071 4 "charged secondaries: costheta distribution"
0072 5 "neutral secondaries: energy spectrum"
0073 6 "neutral secondaries: costheta distribution"
0074
0075 The histograms are managed by the HistoManager class and its Messenger.
0076 The histos can be individually activated with the command :
0077 /analysis/h1/set id nbBins valMin valMax unit
0078 where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
0079
0080 One can control the name of the histograms file with the command:
0081 /analysis/setFileName name (default testem14)
0082
0083 It is possible to choose the format of the histogram file : root (default),
0084 hdf5, xml, csv, by changing the default file type in HistoManager.cc
0085
0086 It is also possible to print selected histograms on an ascii file:
0087 /analysis/h1/setAscii id
0088 All selected histos will be written on a file name.ascii (default testem14)
0089
0090 6- VISUALIZATION
0091
0092 The Visualization Manager is set in the main().
0093 The initialisation of the drawing is done via the commands
0094 /vis/... in the macro vis.mac. To get visualisation:
0095 > /control/execute vis.mac
0096
0097 The detector has a default view which is a longitudinal view of the
0098 box.
0099
0100 The tracks are drawn at the end of event, and erased at the end of run.
0101
0102 7- HOW TO START ?
0103
0104 execute TestEm14 in 'batch' mode from macro files :
0105 % TestEm14 compt.mac
0106
0107 execute TestEm14 in 'interactive mode' with visualization :
0108 % TestEm14
0109 Idle> control/execute vis.mac
0110 ....
0111 Idle> type your commands
0112 ....
0113 Idle> exit
0114
0115 Macros provided in this example:
0116 - anni.mac: e+ (100 MeV) on Aluminium
0117 - atomicDeexcitation: gamma (80 keV) on Tellurium
0118 - compton.mac: gamma (300 keV) on Aluminium
0119 - conv.mac: gamma (20 MeV) on Lead
0120 - convtomu.mac: gamma (100 TeV) on Iron
0121 - electron.mac: e- (100 MeV) on Aluminium
0122 - gamma.mac: gamma (100 keV) on Water
0123 - photoelec.mac: gamma (80 keV) on Gold
0124 - proton.mac: proton (100 MeV) on Water
