medical/fanoCavity/README.md

0001 \page ExamplefanoCavity Example fanoCavity
0002
0003  This program computes the dose deposited in an ionization chamber by a
0004  monoenergetic photon beam.
0005  The geometry of the chamber satisfies the conditions of charged particle
0006  equilibrium. Hence, under idealized conditions, the ratio of the dose
0007  deposited over the beam energy fluence must be equal to the
0008  mass_energy_transfer coefficient of the wall material.
0009
0010  E.Poon and al, Phys. Med. Biol. 50 (2005) 681 \n
0011  I.Kawrakow, Med. Phys. 27-3 (2000) 499 \n
0012
0013 ## GEOMETRY
0014
0015  The chamber is modelized as a cylinder with a cavity in it.
0016
0017  6 parameters define the geometry :
0018    - the material of the wall of the chamber
0019    - the radius of the chamber and the thickness of the wall
0020    - the material of the cavity
0021    - the radius and the thickness of the cavity
0022
0023  Wall and cavity must be made of the same material, but with different
0024  density
0025
0026  All above parameters can be redifined via the UI commands built in
0027  DetectorMessenger class
0028 <pre>
0029                     -----------------
0030                     |               |
0031                     | wall          |
0032                     |     -----     |
0033                     |     |   |     |
0034                     |     | <-+-----+--- cavity
0035          ------>    |     |   |     |
0036          ------>    |     |   |     |
0037    beam     -------------------------------- cylinder axis
0038          ------>    |     |   |     |
0039          ------>    |     |   |     |
0040                     |     |   |     |
0041                     |     |   |     |
0042                     |     -----     |
0043                     |               |
0044                     |               |
0045                     -----------------
0046
0047 </pre>
0048
0049 ## BEAM
0050
0051  Monoenergetic incident photon beam is uniformly distribued, perpendicular
0052  to the flat end of the chamber. The beam radius can be controled with an
0053  UI command built in PrimaryGeneratorMessenger; the default is full wall
0054  chamber radius.
0055
0056  Beam regeneration : after each Compton interaction, the scattered photon is
0057  reset to its initial state, energy and direction. Consequently, interaction
0058  sites are uniformly distribued within the wall material.
0059
0060  This modification must be done in the ParticleChange of the final state
0061  of the Compton scattering interaction. Therefore, a specific model
0062  (MyKleinNishinaCompton) is assigned to the ComptonScattering process in
0063  PhysicsList. MyKleinNishinaCompton inherites from G4KleinNishinaCompton;
0064  only the function SampleSecondaries() is overwritten.
0065
0066 ## PURPOSE OF THE PROGRAM
0067
0068  The program computes the dose deposited in the cavity and the ratio
0069  Dose/Beam_energy_fluence. This ratio is compared to the mass_energy_transfer
0070  coefficient of the wall material.
0071
0072  The mass_energy_transfer coefficient needs :
0073  - the photon total cross section, which is read from the PhysicsTables
0074  by G4EmCalculator (see EndOfRunAction).
0075  - the average kinetic energy of charged secondaries generated in the
0076  wall during the run.
0077
0078  The program needs high statistic to reach precision on the computed dose.
0079  The UI command /testem/event/printModulo allows to survey the convergence of
0080  the kineticEnergy and dose calculations.
0081
0082  In addition, to increase the program efficiency, the secondary particles
0083  which have no chance to reach the cavity are immediately killed (see
0084  StackinAction). This feature can be switched off by an UI command (see
0085  StackingMessenger).
0086
0087  The simplest way to study the effect of e- tracking parameters on dose
0088  deposition is to use the command /testem/stepMax.
0089
0090 ## PHYSICS
0091
0092  The physics lists contains the standard electromagnetic processes, with few
0093  modifications listed here.
0094
0095  - Compton scattering : as explained above, the final state is modified in
0096  MyKleinNishinaCompton class.
0097  \n\n
0098  In order to make the program more efficient, one can increase the Compton
0099  cross section via the function SetCSFactor(factor) and its
0100  associated UI command. Default is factor=1000.
0101
0102  - Bremsstrahlung : Fano conditions imply no energy transfer via
0103  bremsstrahlung radiation. Therefore this process is not registered in the
0104  physics list. However, it is always possible to include it.
0105  See PhysListEmStandard class.
0106
0107  - Ionisation : In order to have same stopping power in wall and cavity, one
0108  must cancel the density correction term in the dedx formula. This is done in
0109  a specific MollerBhabha model (MyMollerBhabhaModel) which inherites from
0110  G4MollerBhabhaModel.
0111  \n\n
0112  To prevent explicit generation of delta-rays, the default production
0113  threshold (i.e. cut) is set to 10 km (CSDA condition).
0114  \n\n
0115  The finalRange of the step function is set to 10 um, which more on less
0116  correspond to a tracking cut in water of about 20 keV. See emOptions.
0117  Once again, the above parameters can be controled via UI commands.
0118
0119  - Multiple scattering : is switched in single Coulomb scattering mode near
0120  boundaries. This is selected via EM options in PhysicsList, and can be
0121  controled with UI commands.
0122
0123  - All PhysicsTables are built with 100 bins per decade.
0124
0125 ## HISTOGRAMS
0126
0127   fanoCavity has several predefined 1D histograms :
0128   -  1 : emission point of e+-
0129   -  2 : energy spectrum of e+-
0130   -  3 : theta distribution of e+-
0131   -  4 : emission point of e+- hitting cavity
0132   -  5 : energy spectrum of e+- when entering in cavity
0133   -  6 : theta distribution of e+- before enter in cavity
0134   -  7 : theta distribution of e+- at first step in cavity
0135   -  8 : track segment of e+- in cavity
0136   -  9 : step size of e+- in wall
0137   - 10 : step size of e+- in cavity
0138   - 11 : energy deposit in cavity per track
0139
0140   The histograms are managed by G4AnalysisManager class and its messenger.
0141   The histos can be individually activated with the command :
0142 ```
0143 /analysis/h1/set id nbBins  valMin valMax unit
0144 ```
0145   where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
0146
0147    One can control the name of the histograms file with the command:
0148 ```
0149 /analysis/setFileName  name  (default fanoCavity)
0150 ```
0151
0152    It is possible to choose the format of the histogram file : root (default),
0153    hdf5, xml, csv, by changing the default file type in HistoManager.cc
0154
0155    It is also possible to print selected histograms on an ascii file:
0156 ```
0157 /analysis/h1/setAscii id
0158 ```
0159    All selected histos will be written on a file name.ascii (default fanocavity)
0160
0161 ## HOW TO START ?
0162
0163  - Execute fanoCavity in 'batch' mode from macro files
0164 ```
0165 % ./fanoCavity   run01.mac
0166 ```
0167
0168  - Alternative macro file:
0169 ```
0170    basic.mac - disabled multiple scattering and fluctuations of energy loss
0171 ```
0172
0173
0174  - Execute fanoCavity in 'interactive mode' with visualization
0175 ```
0176 % ./fanoCavity
0177 ....
0178 Idle> type your commands
0179 ....
0180 Idle> exit
0181 ```