Gabriele Cosmo
130 lines
3.6 KiB
Markdown
130 lines
3.6 KiB
Markdown
\page ExamplePol01 Example Pol01
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How to compute and plot the QED processes including
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polarization.
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Two possible scenarios are available:
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- Polarization transfer of an incoming beam to final state particles
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- Material dependent transmission of a polarized beams.
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The method is explained below : see item Physics.
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## GEOMETRY DEFINITION
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The geometry consists of a single block of a homogeneous material,
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placed in a world.
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Three parameters define the geometry :
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- the material of the box,
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- the thickness of the box (sizeZ),
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- the transverse dimension of the box (sizeXY).
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The default geometry (5mm of Iron, G4_Fe) is constructed in
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DetectorConstruction, but the above parameters can be changed
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interactively via the commands defined in DetectorMessenger.
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Its polarization can be accessed via the G4PolarizationMessenger
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(see example macro file), and is given in the global coordinate
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system.
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## PHYSICS LIST
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The physics list (PhysicsList) contains QED particle definitions (electrons,
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positrons and photons) and a general transportation process.
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In addition the user can add one of the two process modules:
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- 1. "standard" - standard (unpolarized) EM physics
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- 2. "polarized" - polarized EM physics
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These physics list contain the standard electromagnetic processes.
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## AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting
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at the edge of the box. The type of the particle and its
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energy are set in PrimaryGeneratorAction (10 MeV electron).
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By default the G4ParticleGun polarization is zero.
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All parameter can be changed via the G4 build-in commands of
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ParticleGun class (see the macros provided with this example).
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## PHYSICS
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This example uses the following physics processes:
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- electromagnetic:
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- photo-electric effect
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- Compton scattering
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- pair production
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- bremsstrahlung
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- ionization
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- multiple scattering
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- annihilation
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or
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- polarized electromagnetic:
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(incl. simulation of polarization transfer, and
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asymmetries for longitudinally polarized leptons, and
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circularly polarized photons)
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- polarized photo-electric effect
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- polarized Compton scattering
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- polarized pair production
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- polarized bremsstrahlung
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- polarized ionization
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- multiple scattering
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- polarized annihilation
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and
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- transportation
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and defines the following particles:
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electron, positron, photon
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## HISTOGRAMS
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The test contains 12 built-in 1D histograms, which are managed by G4AnalysisManager.
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The histos can be individually activated with the command :
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```
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/analysis/h1/set id nbBins valMin valMax unit
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```
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where unit is the desired unit for the histo (MeV or keV, etc..)
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(see the macro histos.mac).
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- 1 gamma energy
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- 2 gamma cos(theta)
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- 3 gamma phi
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- 4 gamma polarization
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- 5 electron energy
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- 6 electron cos(theta)
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- 7 electron phi
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- 8 electron polarization
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- 9 positron energy
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- 10 positron cos(theta)
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- 11 positron phi
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- 12 positron polarization
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## VISUALIZATION
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Simulated events can be displayed on top of a representation of
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the geometry, see vis.mac for an example.
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## HOW TO START ?
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- Execute Pol01 in 'batch' mode from the default macro file :
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```
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% ./Pol01 pol01.in
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```
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- Execute Pol01 in 'batch' mode including analysis output :
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```
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% ./Pol01 histos.mac
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```
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- If available use JAIDA to display the results via
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```
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% gmake plots
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```
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- A visualisation example is available by calling
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```
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% ./Pol01
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[...]
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PreInit> /control/execute vis.mac
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```
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