Warning, /geant4/examples/advanced/gammaray_telescope/README is written in an unsupported language. File is not indexed.
0001 -------------------------------------------------------------------
0002
0003 =========================================================
0004 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
0005 =========================================================
0006
0007 gammaray_telescope
0008 ------------------
0009 F. Longo, R. Giannitrapani & G. Santin
0010 June 2003
0011
0012 ---------------------------------------------------------------
0013 Acknowledgments to GEANT4 people, in particular to R. Nartallo,
0014 A. Pfeiffer, M. G. Pia and G. Cosmo
0015 ---------------------------------------------------------------
0016
0017 GammaRayTel is an example of application of Geant4 in a space
0018 environment. It simulates a typical telescope for gamma ray analysis;
0019 the detector setup is composed by a tracker made with silicon planes,
0020 subdivided in ladders and strips, a CsI calorimeter and an
0021 anticoincidence system. In this version, the three detectors are made
0022 sensitive but only the hits on the tracker strips are registered and relevant
0023 information (energy deposition, position etc.) are dumped to an external
0024 ASCII file for subsequent analysis.
0025
0026 Relevant information from the simulation is processed in the GammarayTelAnalysis
0027 class and saved, through the G4AnalysisManager interface, to Histograms and
0028 Tuples.
0029
0030 a) Macros for the visualization of geometry and tracks with
0031 OpenGL, VRML and DAWN drivers
0032
0033 b) Implementation of messengers to change some parameters of
0034 the detector geometry, the particle generator and the analysis
0035 manager (if present) runtime
0036
0037 c) Readout geometry mechanism to describe an high number of
0038 subdivisions of the planes of the tracker (strips) without
0039 affecting in a relevant way the simulation performances
0040
0041 d) Histogramming facilities are presently provided through the G4AnalysisManager class.
0042
0043 e) User interfaces via Xmotif or normal terminal provided
0044
0045
0046 1. Setting up the environment variables
0047 ---------------------------------------
0048
0049 - Setup for storing ASCII data
0050
0051 If you want to store the output data in an ASCII file 'Tracks_x.dat'
0052 where x stays for the run number. You should specify the environment
0053 variable:
0054
0055 setenv G4STORE_DATA 1
0056
0057 - Setup for Visualization
0058
0059 IMPORTANT: be sure that your Geant4 installation has been done
0060 with the proper visualization drivers; for details please see the
0061 file geant4/source/visualization/README.
0062
0063 To use the visualization drivers set the following variables in
0064 your local environment:
0065
0066 setenv G4VIS_USE_OPENGLX 1 # OpenGL visualization
0067 setenv G4VIS_USE_DAWNFILE 1 # DAWN file
0068 setenv G4VIS_USE_VRMLFILE 1 # VRML file
0069 setenv G4VRMLFILE_VIEWER vrmlview # If installed
0070
0071 - Setup for Xmotif user interface
0072
0073 setenv G4UI_USE_XM 1
0074
0075 - Set up for analysis
0076
0077 To compile the GammaRayTel example with the analysis tools activated,
0078 set the following variables
0079
0080 setenv G4ANALYSIS_USE 1 # Use the analysis tools
0081
0082 2. Sample run
0083 -------------
0084
0085 To run a sample simulation with gamma tracks interacting with
0086 the detector in its standard configuration and without any
0087 visualization, execute the following command in the example main
0088 directory:
0089
0090 $G4WORKDIR/bin/$G4SYSTEM/GammaRayTel
0091
0092 It is possible also to run three different configuration defined in
0093 macro1.mac, macro2.mac and macro3.mac for visualization (OpenGL, VRML
0094 and DAWN respectively) with the following command
0095
0096 $G4WORKDIR/bin/$G4SYSTEM/GammaRayTel macroX.mac
0097
0098 where X can be 1, 2 or 3. Be sure to have the right environment (see
0099 the preceding section) and the proper visualization driver enabled in
0100 your local G4 installation (see geant4/source/visualization/README for
0101 more information).
0102
0103
0104 3. Detector description
0105 -----------------------
0106
0107 The detector is defined in GammaRayTelDetectorConstruction.cc
0108 It is composed of a Payload with three main detectors, a Tracker (TKR), a
0109 Calorimeter (CAL) and an Anticoincidence system (ACD).
0110
0111 The standard configuration is made of a TKR of 15 Layers of 2 views made of
0112 4 * 4 Si single sided silicon detectors with Lead converter, and a CAL of
0113 5 layers of CsI, each made of 2 views of 12 CsI bars orthogonally posed.
0114 4 lateral panels and a top layer of plastic scintillator (ACL and ACT)
0115 complete the configuration.
0116 The Si detectors are composed of two silicon planes subdivided in strips
0117 aligned along the X axis in one plane and along the Y axis for the other.
0118
0119 The following baseline configuration is adopted:
0120
0121 GEOMETRICAL PARAMETER VALUE
0122
0123 Converter Thickness 300 micron
0124 Silicon Thickness 400 micron
0125 Silicon Tile Size XY 9 cm
0126 Silicon Pitch 200. micrometer
0127 Views Distance 1. mm
0128 CAL Bar Thickness 1.5 cm
0129 ACD Thickness 1. cm
0130
0131 It is possible to modify in some way this configuration using the
0132 commands defined in GammaRayTelDetectorMessenger.
0133 This feature is available in the UI through the commands subtree
0134 "/payload/" (see the help command in the UI for more information).
0135
0136 4. Physics processes
0137 --------------------
0138
0139 This example uses a modular physics list, with a sample of Hadronic processes
0140 (see the web page http://cmsdoc.cern.ch/~hpw/GHAD/HomePage/ for more adeguate
0141 physics lists), the Standard or the LowEnergy Electromagnetic processes.
0142
0143 5. Particle Generator
0144 ---------------------
0145
0146 The GammaRayTelParticleGenerationAction and its Messenger let the user define
0147 the incident flux of particles, from a specific direction or from an
0148 isotropic background. In the first case particles are generated on a spherical
0149 surface which diameter is perpendicular to the arrival direction. In the second
0150 case the arrival directions are isotropic.
0151
0152 The user can define also between two spectral options:
0153 monochromatic or with a power-law dependence. The particle
0154 generator parameters are accessible through the UI tree "/gun/" (use the
0155 UI help for more information). We are planning to include, in the next
0156 releases of this example, the General Particle Source module of G4.
0157
0158 6. Hit
0159 ------
0160
0161 In this version the hits from the TKR the CAL and the ACD are generated.
0162 Only the hit from the TRK are saved. Each TKR hit contains the following
0163 information
0164
0165 a) ID of the event (this is important for multiple events run)
0166 b) Energy deposition of the particle in the strip (keV)
0167 c) Number of the strip
0168 d) Number of the plane
0169 e) Type of the plane (1=X 0=Y)
0170 f) Position of the hit (x, y, z) in the reference frame of the payload
0171
0172 The hit information are saved on an ASCII file named Tracks_N.dat, where
0173 N is the progressive ID number associated to the run.
0174
0175 7. Analysis
0176 -----------
0177
0178 Relevant information from the simulation is processed in the GammarayTelAnalysis
0179 class and saved, through the G4AnalysisManager interface, to Histograms and
0180 Tuples. The output file is written in ROOT format, but one can easily switch to
0181 XML (or Hbook) by changing the appropriate #include in GammarayTelAnalysis.hh
0182 No external software is required (apart from the hbook case, in which the CERNLIB
0183 must be installed and a FORTRAN compiler must be present)
0184
0185 Keep in mind that the actual implementation of the analysis tools in GammaRayTel
0186 is of a pedagogical nature, so we kept it as simple as possible.
0187
0188 The actual analysis produces some histograms (see next section) and an ntuple.
0189 Both the histograms and the ntuple are saved at the end of the run in the file
0190 "gammaraytel.root". Please note that in a multiple run session,
0191 the last run always override the root file.
0192
0193 8. Histogramming
0194 ----------------
0195
0196 The 1D histograms contain the energy deposition in the last X plane of
0197 the TKR and the hits distribution along the X planes of the TKR
0198 (note again that these histograms have been chosen more for pedagogical
0199 motivation than for physical one).
0200
0201 These histograms are filled and updated at every event and are initialized
0202 with each new run; the scale of the histograms is automatically derived from
0203 the detector geometry.
0204
0205 Through a messenger it is possible to set some options with
0206 the UI subtree "/analysis/" (use the UI help for more info);
0207
0208 In this example we only show the use of very basic feature of this new
0209 simulation/analysis framework.
0210
0211 9. Digi
0212 -------
0213
0214 For the TKR also the digits corresponding to the Hits are generated.
0215 A digi is generated when the hit energy deposit is greater than a threshold
0216 (in this example setted at 120 keV).
0217 The TKR digi information are stored on the same file Tracks_N.dat and contain:
0218
0219 a) ID of the event (this is important for multiple events run)
0220 b) Number of the strip
0221 c) Number of the plane
0222 d) Type of the plane (1=X 0=Y)
0223
0224 10. Classes Overview
0225 --------------------
0226
0227 This is the overview of the classes defined in this example
0228
0229 GammaRayTelPrimaryGeneratorAction
0230 User action for primaries generator
0231
0232 GammaRayTelPrimaryGeneratorMessenger
0233 Messenger for interactive particle generator
0234 parameters modification via the User Interface
0235
0236 GammaRayTelPhysicsList
0237 Determination of modular physics classes
0238
0239 GammaRayTelDetectorConstruction
0240 Geometry and material definitions for the detector
0241
0242 GammaRayTelDetectorMessenger
0243 Messenger for interactive geometry parameters
0244 modification via the User Interface
0245
0246 GammaRayTelAnalysis
0247 Analysis manager class (experimental)
0248
0249 GammaRayTelAnalysisMessenger
0250 Messenger for interactive analysis options modification
0251 via the User Interface
0252
0253 GammaRayTelRunAction
0254 User run action class
0255
0256 GammaRayTelEventAction
0257 User event action class
0258
0259 GammaRayTelTrackerHit
0260 Description of the hits on the tracker
0261
0262 GammaRayTelDigi
0263 Description of the digi on the tracker
0264
0265 GammaRayTelDigitizer
0266 Description of the digitizer for the tracker
0267
0268 GammaRayTelTrackerSD
0269 Description of the TKR sensitive detector
0270
0271 GammaRayTelAnticoincidenceHit
0272 Description of the hits on the anticoincidence
0273
0274 GammaRayTelAnticoincidenceSD
0275 Description of the ACD sensitive detector
0276
0277 GammaRayTelCalorimeterHit
0278 Description of the hits on the calorimeter
0279
0280 GammaRayTelCalorimeterSD
0281 Description of the CAL sensitive detector
