| [807] | 1 | $Id: README,v 1.4 2006/05/15 14:42:42 maire Exp $
|
|---|
| 2 | -------------------------------------------------------------------
|
|---|
| 3 |
|
|---|
| 4 | =========================================================
|
|---|
| 5 | Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
|---|
| 6 | =========================================================
|
|---|
| 7 |
|
|---|
| 8 | TestEm13
|
|---|
| 9 | --------
|
|---|
| 10 |
|
|---|
| 11 | How to compute cross sections from the tramsmition coefficient
|
|---|
| 12 | ( see below, item Physics).
|
|---|
| 13 |
|
|---|
| 14 | 1- GEOMETRY DEFINITION
|
|---|
| 15 |
|
|---|
| 16 | It is a single box representing a layer of finite thickness of
|
|---|
| 17 | homogeneous material.
|
|---|
| 18 | Two parameters define the geometry :
|
|---|
| 19 | - the material of the box,
|
|---|
| 20 | - the (full) size of the box.
|
|---|
| 21 |
|
|---|
| 22 | The default geometry (1 cm of water) is constructed in
|
|---|
| 23 | DetectorConstruction, but the above parameters can be changed
|
|---|
| 24 | interactively via the commands defined in DetectorMessenger.
|
|---|
| 25 |
|
|---|
| 26 | 2- PHYSICS LIST
|
|---|
| 27 |
|
|---|
| 28 | The physics list contains the standard electromagnetic processes.
|
|---|
| 29 | In order not to introduce 'articicial' constraints on the step size, the
|
|---|
| 30 | multiple scattering is not instanciated, and there is no limitation from
|
|---|
| 31 | the maximum energy lost per step.
|
|---|
| 32 |
|
|---|
| 33 | 3- AN EVENT : THE PRIMARY GENERATOR
|
|---|
| 34 |
|
|---|
| 35 | The primary kinematic consists of a single particle starting at the edge
|
|---|
| 36 | of the box. The type of the particle and its energy are set in
|
|---|
| 37 | PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
|
|---|
| 38 | build-in commands of ParticleGun class (see the macros provided with
|
|---|
| 39 | this example).
|
|---|
| 40 |
|
|---|
| 41 | 4- PHYSICS
|
|---|
| 42 |
|
|---|
| 43 | An event is killed at the first step of the incident paticle.
|
|---|
| 44 | Either the particle has interacted or is transmitted through the layer.
|
|---|
| 45 | The cross section, also called absorption coefficient, is computed from
|
|---|
| 46 | the rate of unaltered transmitted incident particles.
|
|---|
| 47 |
|
|---|
| 48 | The result is compared with the 'input' data, i.e. with the cross
|
|---|
| 49 | sections stored in the PhysicsTables and used by Geant4.
|
|---|
| 50 |
|
|---|
| 51 | A set of macros defining various run conditions are provided.
|
|---|
| 52 | The processes are actived/inactived in order to survey the processes
|
|---|
| 53 | individually.
|
|---|
| 54 |
|
|---|
| 55 |
|
|---|
| 56 | 6- VISUALIZATION
|
|---|
| 57 |
|
|---|
| 58 | The Visualization Manager is set in the main().
|
|---|
| 59 | The initialisation of the drawing is done via the commands
|
|---|
| 60 | /vis/... in the macro vis.mac. To get visualisation:
|
|---|
| 61 | > /control/execute vis.mac
|
|---|
| 62 |
|
|---|
| 63 | The detector has a default view which is a longitudinal view of the
|
|---|
| 64 | box.
|
|---|
| 65 |
|
|---|
| 66 | The tracks are drawn at the end of event, and erased at the end of run.
|
|---|
| 67 |
|
|---|
| 68 | 7- HOW TO START ?
|
|---|
| 69 |
|
|---|
| 70 | compile and link to generate an executable
|
|---|
| 71 | % cd geant4/examples/extended/electromagnetic/TestEm13
|
|---|
| 72 | % gmake
|
|---|
| 73 |
|
|---|
| 74 | execute TestEm13 in 'batch' mode from macro files :
|
|---|
| 75 | % TestEm13 compt.mac
|
|---|
| 76 |
|
|---|
| 77 | execute TestEm13 in 'interactive mode' with visualization :
|
|---|
| 78 | % TestEm13
|
|---|
| 79 | Idle> control/execute vis.mac
|
|---|
| 80 | ....
|
|---|
| 81 | Idle> type your commands
|
|---|
| 82 | ....
|
|---|
| 83 | Idle> exit
|
|---|
| 84 |
|
|---|
