1 | $Id: README,v 1.1 2002/03/05 15:21:55 gcosmo Exp $ |
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2 | ------------------------------------------------------------------- |
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3 | |
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4 | ========================================================= |
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5 | Geant4 - an Object-Oriented Toolkit for Simulation in HEP |
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6 | ========================================================= |
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7 | |
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8 | ParN02 |
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9 | ------ |
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10 | |
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11 | |
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12 | This example simulates a simplified fixe target experiment. |
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13 | Read 000README for a description of how to run it in parallel. |
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14 | |
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15 | 1- GEOMETRY DEFINITION |
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16 | |
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17 | The setup consists of a target followed by six chambers of increasing |
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18 | transverse size. These chambers are located in a region called Tracker |
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19 | region. Their shape are boxes, constructed as parametrised volumes |
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20 | (ChamberParametrisation class). |
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21 | |
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22 | The default geometry is constructed in DetectorConstruction class. |
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23 | One can change the material of the target and of the chambers |
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24 | interactively via the commands defined in the DetectorMessenger class. |
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25 | |
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26 | In addition a transverse uniform magnetic field can be applied (see |
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27 | N02MagneticField and DetectorMessenger classes). |
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28 | |
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29 | |
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30 | 2- PHYSICS LIST |
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31 | |
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32 | The particle's type and the physic processes which will be available |
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33 | in this example are set in PhysicsList class. |
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34 | |
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35 | In this example, all the so called 'electromagnetic processes' are |
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36 | introduced for gamma, charged leptons, and charged hadrons (see the |
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37 | method PhysicsList::ConstructEM()). |
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38 | |
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39 | An important data member of this class is the defaultCutValue which |
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40 | defines the production threshold of secondary particles |
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41 | (mainly Ionisation and Bremsstrahlung processes are concerned by this |
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42 | CutValue). |
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43 | Notice that the CutValue must be given in unit of length, corresponding |
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44 | to the stopping range of the particle. It is automatically converted |
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45 | in energy for each material, and a table is printed in the method |
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46 | PhysicsList::SetCuts() |
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47 | |
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48 | In addition the build-in interactive command: |
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49 | /process/(in)activate processName |
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50 | allows to activate/inactivate the processes one by one. |
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51 | |
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52 | |
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53 | 3- RUNS and EVENTS |
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54 | |
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55 | The primary kinematic consists of a single particle which hits the |
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56 | target perpendicular to the input face. The type of the particle |
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57 | and its energy are set in the PrimaryGeneratorAction class, and can |
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58 | be changed via the G4 build-in commands of ParticleGun class. |
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59 | |
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60 | A RUN is a set of events. |
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61 | |
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62 | The user has control: |
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63 | -at Begin and End of each run (class RunAction) |
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64 | -at Begin and End of each event (class EventAction) |
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65 | -at Begin and End of each track (class TrackingAction, not used here) |
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66 | -at End of each step (class SteppingAction) |
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67 | |
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68 | The class SteppingVerbose prints some informations step per step, |
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69 | under the control of the command: /tracking/verbose 1 |
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70 | It inherits from G4SteppingVerbose, and has been setup here in order |
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71 | to illustrate how to extract informations from the G4 kernel during |
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72 | the tracking of a particle. |
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73 | |
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74 | |
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75 | 4- DETECTOR RESPONSE |
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76 | |
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77 | A HIT is a record, track per track (even step per step), of all the |
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78 | informations needed to simulate and analyse the detector response. |
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79 | |
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80 | In this example the Tracker chambers are considered as the detector. |
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81 | Therefore the chambers are declared 'sensitive detectors' (SD) in |
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82 | the DetectorConstruction class. |
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83 | |
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84 | Then, a Hit is defined as a set of 4 informations per step, inside |
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85 | the chambers, namely: |
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86 | - the track identifier (an integer), |
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87 | - the chamber number, |
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88 | - the total energy deposit in this step, |
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89 | - the position of the deposit. |
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90 | |
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91 | A given hit is an instance of the class TrackerHit which is created |
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92 | during the tracking of a particle, step by step, in the method |
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93 | TrackerSD::ProcessHits(). This hit is inserted in a HitsCollection. |
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94 | |
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95 | The HitsCollection is printed at the end of event (via the method |
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96 | TrackerSD::EndOfEvent()), under the control of the command: /hits/verbose 1 |
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97 | |
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98 | |
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99 | 5- VISUALIZATION |
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100 | |
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101 | The Visualization Manager is set in the main(). |
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102 | The initialisation of the drawing is done via a set of /vis/ commands |
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103 | in the macro vis.mac. This macro is automatically read from |
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104 | the main when running in interactive mode. |
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105 | |
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106 | The tracks are automatically drawn at the end of event and erased at |
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107 | the beginning of the next run. |
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108 | |
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109 | The visualization (with OpenGL driver) assumes two things: |
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110 | 1- the visualisation & interfaces categories have been compiled |
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111 | with the environment variable G4VIS_BUILD_OPENGLX_DRIVER. |
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112 | 2- ParN02.cc has been compiled with G4VIS_USE_OPENGLX. |
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113 | |
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114 | (The same with DAWNFILE instead of OPENGLX) |
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115 | |
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116 | |
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117 | 6- USER INTERFACES |
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118 | |
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119 | The default command interface, called G4UIterminal, is done via |
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120 | standart cin/G4cout. |
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121 | On Linux and Sun-cc on can use a smarter command interface G4UItcsh. |
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122 | It is enough to set the environment variable G4UI_USE_TCSH before |
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123 | compiling ParN02.cc |
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124 | |
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