$Id: README,v 1.33 2009/09/17 20:06:26 maire Exp $ ------------------------------------------------------------------- ========================================================= Geant4 - an Object-Oriented Toolkit for Simulation in HEP ========================================================= TestEm3 ------- How to collect energy deposition in a sampling calorimeter. How to survey energy flow. how to print stopping power. 1- GEOMETRY DEFINITION The calorimeter is a box made of a given number of layers. A layer consists of a sequence of various absorbers (maximum MaxAbsor=9). The layer is replicated. Parameters defining the calorimeter : - the number of layers, - the number of absorbers within a layer, - the material of the absorbers, - the thickness of the absorbers, - the transverse size of the calorimeter (the input face is a square). 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 modified interactively via the commands defined in the DetectorMessenger class. |<----layer 0---------->|<----layer 1---------->|<----layer 2---------->| | | | | ========================================================================== || | || | || | || || | || | || | || || abs 1 | abs 2 || abs 1 | abs 2 || abs 1 | abs 2 || || | || | || | || || | || | || | || beam || | || | || | || ======> || | || | || | || || | || | || | || || | || | || | || || | || | || | || || | || | || | || || cell 1 | cell 2|| cell 3 | cell 4|| cell 5 | cell 6|| ========================================================================== ^ ^ ^ ^ ^ ^ ^ pln1 pln2 pln3 pln4 pln5 pln6 pln7 NB. The number of absorbers and the number of layers can be set to 1. In this case we have a unique homogeneous block of matter, which looks like a bubble chamber rather than a calorimeter ... (see the macro of commands: newgeom.mac) 2- PHYSICS LISTS 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 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 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 calorimeter perpendicular to the input face. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can be changed via the G4 build-in commands of ParticleGun class (see the macros provided with this example). In addition one can choose randomly the impact point of the incident particle. The corresponding interactive command is built in PrimaryGeneratorMessenger. A RUN is a set of events. TestEm3 computes the energy deposited per absorber and the energy flow through the calorimeter 4- VISUALIZATION The Visualization Manager is set in the main(). The initialisation of the drawing is done via the commands : /vis/... in the macro vis.mac. In interactive session: PreInit or Idle > /control/execute vis.mac The default view is a longitudinal view of the calorimeter. 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. 5- PHYSICS DEMO The particle's type and the physic processes which will be available in this example are set in PhysicsList class. In addition a build-in interactive command (/process/inactivate processName) allows to activate/inactivate the processes one by one. Then one can well visualize the processes one by one, especially in the bubble chamber setup with a transverse magnetic field. As a homework try to visualize a gamma conversion alone, or the effect of the multiple scattering. Notice that one can control the maximum step size in each absorber, via the StepMax process and the command /testem/stepMax/absorber (see StepMax and PhysicsList classes) 6- HOW TO START ? - compile and link to generate an executable % cd TestEm3 % gmake - execute TestEm3 in 'batch' mode from macro files % TestEm3 run01.mac - execute TestEm3 in 'interactive mode' with visualization % TestEm3 .... Idle> type your commands. For instance: Idle> /control/execute run01.mac .... Idle> exit 7- HISTOGRAMS Testem3 can produce histograms : histo 1 : energy deposit in absorber 1 histo 2 : energy deposit in absorber 2 ...etc........... One can control the binning of the histo with the command: /testem/histo/setHisto idAbsor nbin Emin Emax unit ...etc........... where unit is the desired energy unit for that histo (see TestEm3.in). histo 11 : longitudinal profile of energy deposit in absorber 1 (MeV/event) histo 12 : longitudinal profile of energy deposit in absorber 2 (MeV/event) ...etc........... histo 21 : energy flow (MeV/event) histo 22 : lateral energy leak (MeV/event) One can control the name of the histograms file with the commands: /testem/histo/setFileName name (default testem3) /testem/histo/setFileType type (choice: hbook, root(default), XML) NB. Numbering scheme for histograms: layer : from 1 to NbOfLayers (inclued) absorbers : from 1 to NbOfAbsor (inclued) planes : from 1 to NbOfLayers*NbOfAbsor + 1 (inclued) It is also possible to print selected histograms on an ascii file: /testem/histo/printHisto id All selected histos will be written on a file name.ascii (default testem3) Note that, by default, histograms are disabled. To activate them, uncomment the flag G4ANALYSIS_USE in GNUmakefile. Before compilation of the example it is optimal to clean up old files: gmake histclean gmake 8- USING HISTOGRAMS To use histograms, at least one of the AIDA implementations should be available. See InstallAida.txt