$Id: README,v 1.23 2010/09/17 18:45:43 maire Exp $ ------------------------------------------------------------------- ========================================================= Geant4 - an Object-Oriented Toolkit for Simulation in HEP ========================================================= TestEm7 ------- How to produce a Bragg curve in a water phantom. How to compute the dose in small 'test volumes' called tallies. How to define a maximum step size. 1- GEOMETRY DEFINITION The geometry consists of a single block of a homogenous material, placed in a world. Three parameters define the geometry : - the material of the box, - the thickness of the box (sizeX), - the tranverse dimension of the box (sizeYZ). The default is 20 cm of water. In addition a transverse uniform magnetic field can be applied. The default geometry is constructed in DetectorConstruction class, but all of the above parameters can be changed interactively via the commands defined in the DetectorMessenger class. The size, matter, positions of several test-volumes (tallies) can be defined via UI commands : /testem/det/tally... 2- PHYSICS LIST Physics lists can be local (eg. in this example) or from G4 kernel physics_lists subdirectory. Local physics lists: - "local" standard EM physics with current 'best' options setting. these options are explicited in PhysListEmStandard - "standardSS" standard EM physics with single Coulomb scattering instead of multiple scattering; - "standardNR" standard EM physics with single Coulomb scattering process G4ScreenedNuclearRecoil instead of the multiple scattering for ions with energy less than 100 MeV/nucleon; the new process was developed by M.H. Mendenhall and R.A. Weller from Vanderbuilt University and published in NIM B 277 (2005) 420. In later Geant4 releases the process will be a part of Geant4 source, currently it is released together with its mathematical tool c2_functions in current From geant4/source/physics_lists/builders: - "emstandard_opt0" recommended standard EM physics for LHC - "emstandard_opt1" best CPU performance standard physics for LHC - "emstandard_opt2" - "emstandard_opt3" best current advanced EM options. analog to "local" above - "emlivermore" low-energy EM physics using Livermore data - "empenelope" low-energy EM physics implementing Penelope models Optional components can be added: - "elastic" elastic scattering of hadrons - "HElastic" - "QElastic" - "binary" QBBC configuration of hadron inelastic models - "binary_ion" Binary ion inelastic models Physics lists and options can be (re)set with UI commands Please, notice that options set through G4EmProcessOPtions are global, eg for all particle types. In G4 builders, it is shown how to set options per particle type. 3- AN EVENT : THE PRIMARY GENERATOR The primary kinematic consists of a single particle which hits the block perpendicular to the input face. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can changed via the G4 build-in commands of ParticleGun class (see the macros provided with this example). The default is proton 160 MeV In addition one can define randomly the impact point of the incident particle. The corresponding interactive command is built in PrimaryGeneratorMessenger class. A RUN is a set of events. 4- DOSE IN 'TEST-VOLUMES' The energy deposited in the test-volumes (tallies) defined in DetectorConstruction are printed at EndOfRun, both in MeV and gray. 5- VISUALIZATION The Visualization Manager is set in the main(). The initialisation of the drawing is done via the command > /control/execute vis.mac The detector has a default view which is a longitudinal view of the box. The tracks are drawn at the end of event, and erased at the end of run. Optionaly one can choose to draw all particles, only the charged one, or none. This command is defined in EventActionMessenger class. 6- HOW TO START ? - compile and link to generate an executable % cd geant4/examples/extended/electromagnetic/TestEm7 % gmake - execute Test in 'batch' mode from macro files % TestEm7 proton.mac - execute Test in 'interactive mode' with visualization % TestEm7 .... Idle> type your commands .... Idle> exit 7- HISTOGRAM OF THE BRAGG PEAK Testem7 computes the total energy deposited along the trajectory of the incident particle : the so-called Bragg peak. In order to control the accuracy of the deposition, the user can limit the maximum allowed for the step size of charged particles. (command /testem/stepMax ) The result is a 1D histogram, which is the total energy deposited along the trajectory of the incident particle. The bin size is egal to stepMax. The number of bins is determined by the thickness of the absorber (with a minimum of 100 bins). The total energy deposited is plotted in MeV/mm per incident particle. The next histogram allows to have a zoom around the Bragg peak. Its bining should be defined via UI command: /testem/histo/setHisto 2 nbins xmin xmax unit The last histogram shows the projectile range. Its bining should be defined similary by the UI command: /testem/histo/setHisto 3 nbins xmin xmax unit 8- USING HISTOGRAMS By default the histograms are not activated. To activate histograms the environment variable G4ANALYSIS_USE should be defined. For instance uncomment the flag G4ANALYSIS_USE in GNUmakefile. To use histograms, at least one of the AIDA implementations should be available. See InstallAida.txt Before compilation of the example it is optimal to clean up old files: gmake histclean gmake One can choose the format of the histogram file (hbook, root, XML): /testem/histo/setFileType root The default name "testem7" can be changed: /testem/histo/setFileName myname