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0001 -------------------------------------------------------------------
0002
0003 =========================================================
0004 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
0005 =========================================================
0006
0007 TestEm13
0008 --------
0009
0010 How to compute cross sections from the transmition coefficient
0011 ( see below, item Physics).
0012
0013 1- GEOMETRY DEFINITION
0014
0015 It is a single box representing a layer of finite thickness of
0016 homogeneous material.
0017 Two parameters define the geometry :
0018 - the material of the box,
0019 - the (full) size of the box.
0020
0021 The default geometry (1 cm 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 step of the incident paticle.
0043 Either the particle has interacted or is transmitted through the layer.
0044 The cross section, also called absorption coefficient, is computed from
0045 the rate of unaltered transmitted incident particles.
0046
0047 The result is compared with the 'input' data, i.e. with the cross
0048 sections stored in the PhysicsTables and used by Geant4.
0049
0050 A set of macros defining various run conditions are provided.
0051 The processes are actived/inactived in order to survey the processes
0052 individually.
0053
0054
0055 6- VISUALIZATION
0056
0057 The Visualization Manager is set in the main().
0058 The initialisation of the drawing is done via the commands
0059 /vis/... in the macro vis.mac. To get visualisation:
0060 > /control/execute vis.mac
0061
0062 The detector has a default view which is a longitudinal view of the
0063 box.
0064
0065 The tracks are drawn at the end of event, and erased at the end of run.
0066
0067 7- HOW TO START ?
0068
0069 execute TestEm13 in 'batch' mode from macro files :
0070 % TestEm13 compt.mac
0071
0072 execute TestEm13 in 'interactive mode' with visualization :
0073 % TestEm13
0074 Idle> control/execute vis.mac
0075 ....
0076 Idle> type your commands
0077 ....
0078 Idle> exit
0079
0080 Macros provided in this example:
0081 - anni.mac: e+ (10 MeV) on 5 cm Aluminium
0082 - compton.mac: gamma (300 keV) on 1 cm Aluminium
0083 - conv.mac: gamma (20 MeV) on 5 mm Lead
0084 - electron.mac: e- (100 MeV) on 1 cm Aluminium
0085 - gamma.mac: gamma (100 keV) on 1 cm Water
0086 - photoelec.mac: gamma (100 keV) on 1 cm Iron
0087 - proton.mac: proton (1 GeV) on 1 cm Water
