Gabriele Cosmo
125 lines
4.3 KiB
Plaintext
125 lines
4.3 KiB
Plaintext
$Id: README,v 1.3 2007/01/18 09:07:20 hbu Exp $
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-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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TestEm16
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--------
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Simulate synchrotron radiation
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1- GEOMETRY DEFINITION
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The geometry consists of a single block of a homogenous material.
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Two parameters define the geometry :
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- the material of the box,
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- the (full) size of the box.
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The default is 500 m of vacuum.
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A transverse uniform magnetic field can be applied.
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The default geometry is constructed in DetectorConstruction class,
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but all of the above parameters can be changed interactively via
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the commands defined in the DetectorMessenger class.
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2- PHYSICS LIST
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The particle list is the one of novice/exampleN03 and TestEm6
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with in addition synchrotron radiation.
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To make the synchrotron radiation easily visible, a very low
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pressure "vaccuum" and a magnetic field of by default 1 Tesla
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in z-direction is used.
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle which hits the
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block perpendicular to the input face. The type of the particle
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and its energy are set in the PrimaryGeneratorAction class, and can
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changed via the G4 build-in commands of ParticleGun class (see
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the macros provided with this example).
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The default is an positron of 10 GeV.
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In addition one can choose randomly the impact point of the incident
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particle. The corresponding interactive command is built in
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PrimaryGeneratorMessenger class.
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A RUN is a set of events.
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4- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via the command
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> /control/execute vis.mac
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> /run/beamOn 1
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The detector has a default view which is a longitudinal view of the box.
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The tracks are drawn at the end of event, and erased at the end of run.
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Optionaly one can choose to draw all particles, only the charged one,
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or none. This command is defined in EventActionMessenger class.
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5- PHYSICS DEMO
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The particle's type and the physic processes which will be available
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in this example are set in PhysicsList class.
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In addition a build-in interactive command (/process/inactivate proname)
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allows to activate/inactivate the processes one by one.
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The threshold for producing secondaries can be changed.
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eg: /run/particle/setCut 100 micrometer
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/run/initialize
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To visualize the Synchrotron radiation :
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/control/execute vis.mac
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6- HOW TO START ?
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- compile and link to generate an executable
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% cd geant4/examples/extended/electromagnetic/TestEm16
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% make
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- execute Test in 'batch' mode from macro files
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% TestEm16 run01.mac
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- execute Test in 'interactive mode' with visualization
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% TestEm16
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....
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Idle> type your commands
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....
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Idle> exit
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7 - TRACKING : stepMax and setMaxStepLength
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In order to control the accuracy of the deposition, the user can limit
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'by hand' the maximum step size stepMax of charged particles.
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The maximum tracking step length for computing of magnetic field lines
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is by default set to 1 km.
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Synchrotron radiation in very weak magnetic fields of the order of 1 Gauss
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may require longer pathlength.
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This can be achieved with using setMaxStepLength like
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/testem/tracking/setMaxStepLength 100 km
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8- HISTOGRAMS
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TestEm16 produces 3 histograms which illustrate synchrotron radiation.
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The photon energy spectrum (photons / energy bin) and the power spectrum
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(photon spectrum weighted with the photon energy) and a histogram
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of the path length between photon radiation is produced.
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By default the histograms are not activated. To activate histograms
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the environment variable G4ANALYSIS_USE should be defined. For instance
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uncomment the flag G4ANALYSIS_USE in GNUmakefile.
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Before compilation of the example it is optimal to clean up old files:
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make histclean
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make
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By default the histograms are saved as testem16.hbook
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It is possible to choose the format of the histogram file (hbook, root, XML)
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and the binning using /testem/histo/ command, see run01.mac
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