| Geant4 Cross Reference |
1 ----------------------------------------------------- 2 3 ========================================================= 4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP 5 ========================================================= 6 7 electronScattering 8 ------------------ 9 10 Electron scattering benchmark (T. O'Shea and B. Faddegon) 11 12 1- GEOMETRY DEFINITION 13 14 The geometry is described in the enclosed documument : NRCC_electron_scat.pdf 15 16 A "World" volume contains a "Frame" made of Air. 17 The Frame contains : ExitWindow, ScatterFoil, MonitorChbr, Bag. 18 The Bag contains a Gas volume, which contains 2 aluminium Rings 19 The Scoring plane is the end-plane of the Frame 20 21 The default geometry is constructed in DetectorConstruction class. 22 The parameters of the ScatterFoil (material and thickness) must be defined 23 via 2 UI commands : see the macro scatter.mac 24 25 2- PHYSICS LIST 26 27 Physics lists can be local (eg. in this example) or from G4 kernel 28 physics_lists subdirectory. 29 30 Local physics lists: 31 - "local" standard EM physics with current 'best' options setting. 32 these options are explicited in PhysListEmStandard 33 - "standardSS" standard EM physics with single Coulomb scattering 34 instead of multiple scattering 35 36 From geant4/source/physics_lists/builders: 37 - "emstandard_opt0" recommended standard EM physics for LHC 38 - "emstandard_opt1" best CPU performance standard physics for LHC 39 - "emstandard_opt2" alternative models 40 - "emstandard_opt3" current state of art for EM physics 41 analog to "local"above 42 43 Physics lists and options can be (re)set with UI commands 44 45 Please, notice that options set through G4EmProcessOPtions are global, eg 46 for all particle types. In G4 builders, it is shown how to set options per 47 particle type. 48 49 50 3- PRIMARY GENERATOR : mono-enegetic pencil beam 51 52 The primary kinematic consists of a single particle which hits the detector 53 perpendicular to the input face (ExitWindow). The type of the particle and its 54 energy are set in the PrimaryGeneratorAction class, and can be changed via 55 the G4 build-in commands of ParticleGun class. 56 (see the macros provided with this example) 57 58 The incident beam has a Gaussian-shaped spatial distribution. The rms of the 59 Gaussian can be define with an UI command built in PrimaryGeneratorMessenger. 60 61 4- VISUALIZATION 62 63 The Visualization Manager is set in the main(). 64 The initialisation of the drawing is done via the commands in vis.mac 65 In interactive session: 66 PreInit or Idle > /control/execute vis.mac 67 68 The example has a default view which is a longitudinal view of the detector. 69 70 The tracks are drawn at the end of event, and erased at the end of run. 71 Optionaly one can choose to draw all particles, only the charged, or none. 72 This command is defined in EventActionMessenger class. 73 74 5- TRACKING 75 76 One can limit 'by hand' the step lenght of the particle. As an example, 77 this limitation is implemented as a 'full' process : see StepMax class and its 78 Messenger. The 'StepMax process' is registered in the Physics List. 79 80 6- DETECTOR RESPONSE 81 82 At the end of a run, from the histogram(s), one can study different 83 physics quantities, via the histograms defined below. 84 85 An ascii file corresponding to histo 4 (see below) is automatically written. 86 87 88 7- List of the built-in histograms 89 ---------------------------------- 90 91 The test contains 4 built-in 1D histograms, which are managed by 92 G4AnalysisManager class and its Messenger. The histos can be individually activated 93 with the command : 94 /analysis/h1/set id nbBins valMin valMax unit 95 where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..) 96 (see the macros xxxx.mac). 97 98 1 "(charged particles): projected angle at Scoring plane" 99 2 "(charged particles): dN/dS at Scoring plane" 100 3 "(charged particles): d(N/cost)/dS at Scoring plane" 101 4 "(charged particles): normalized d(N/cost)/dS at Scoring plane" 102 5 "(charged particles); scattering angle theta" 103 6 "(charged particles); measured scattering angle theta" 104 105 The histograms can be viewed using ROOT or PAW. 106 107 One can control the name and format of the histograms file with the command: 108 /analysis/setFileName name (default nrccBenchmark) 109 It is possible to choose the format of the histogram file : root (default), 110 xml, csv, by using namespace in HistoManager.hh 111 It is also possible to print selected histograms on an ascii file: 112 /analysis/h1/setAscii id 113 All selected histos will be written on a file name.ascii (default nrccBenchmark) 114 115 116 8- HOW TO START ? 117 118 - execute electronScattering in 'batch' mode from macro files e.g. 119 % electronScattering myMacro.mac 120 121 - execute electronScattering in 'interactive' mode with visualization e.g. 122 % electronScattering 123 Then type your commands, for instance : 124 Idle> control/execute vis.mac 125 Idle> run/beamOn 5 126 ....