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Forum: Event and Track Management
Re: None Could Geant4 simulate the number of secondary electron in the TPC gas (Anna Wang)
Date: 25 Jan, 2013
From: michel maire <michel maire>

On Mon, 21 Jan 2013 07:30:39 GMT, Anna Wang wrote:
> Hi,
>    I want to simulate  primary ionization distance and the number of secondary electron produced by primary ionization per unit length when a charged particle passes through TPC gas. For TPC gas mixture 70% Ar+30%Isobutant,  at normal condition the average distance between primary ionizations for fast particle should be around 300 um.  
> 
>   But my simulation result is about 1 mm for 500MeV electron  when I set " G4ProductionCutsTable::GetProductionCutsTable()->SetEnergyRange(10*eV, 1*GeV)" in PhysicsList and "/testem/phys/addPhysics livermore". 
> Now I suspect whether Geant4 could simulate the number of secondary electron in the TPC gas 
> 

 I took TestEm1, added in PhysicsList G4ProductionCutsTable::GetProductionCutsTable()->SetEnergyRange(10*eV, 1*GeV)
 and ran following macro

 # Ionisation only
 #
 /control/verbose 2
 /run/verbose 2
 #
 /testem/det/setMat ArgonButane
 /testem/det/setSize 1 cm
 #
 /testem/phys/addPhysics local
 #
 /run/initialize
 #
 # prevent any gamma production
 /testem/phys/setGCut  1 km
 #
 # no multiple scattering
 /process/inactivate msc
 #
 # set cut for ionisation
 /testem/phys/setECut  1 um
 #
 /testem/gun/setDefault
 /gun/particle e-
 /gun/energy 500 MeV
 #
 /analysis/setFileName ionis
 /analysis/h1/set 2 100 0  100 none	#nb steps of primary
 /analysis/h1/set 3 100 0   2000 um	#step size of primary
 /analysis/h1/set 5 100 0   200 eV	#energy of charged secondaries
 #
 /testem/event/printModulo 1000
 #
 /run/beamOn 10000

 Here, only ionisation is active, eg. the step size is detemined by ionisation.
 The plots are in attachement. I hope they are self explanatory.
 - from histo 3, we see all step sizes, from few um, with a mean ~500 um
 - from histo 5, we see the 10 eV production threshold.

 Notice that an alternative to 'normal' ionisation process is the PAI model
 (see example TestEm8)

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/25/11.40-28722-awang.log.txt
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/25/11.40-84278-nbSteps.jpg
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/25/11.40-38205-stepSize.jpg
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/01/25/11.40-12536-energy.jpg

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