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Forum: Event and Track Management
Re: None Sensitive detector to secondary particles (Annette Pressman)
Re: None Re: Sensitive detector to secondary particles (Annette Pressman)
Date: 09 Apr, 2013
From: Marc Verderi <Marc Verderi>

Dear Annette,

     Please let me remind a few basics of how the simulation works.

     Geant4 starts with -say- a primary particle generated by the 
primary generator action. This primary is then tracked, step by step, by 
Geant4. When doing a step, Geant4 invokes all necessary physics 
computation, and leads to:
     - an energy deposit in the current material during this current step
     - a change of energy/momentum of this primary
     - a potential creation of secondary particles, coming from 
interactions during this step.
     This step by step progression continues up to the point the primary 
is killed (by interaction, or leaving the world volume).
     Then one of the produced secondary (by default the last one) is 
taken by Geant4, and this becomes the current primary particle. The same 
above step by step game is played, with secondaries creation, etc. The 
event simulation is finished when the particles (generated by the 
primary generator action, or subsequently by any interactions) have been 
all tracked and finally killed.

     The secondary particles are, as you understood, G4Track objects. 
You can actually know in your G4VSensitiveDetector what are the 
secondary particles produced by the current primary. But please note, at 
the very point it has been created, that you will not be able to get any 
information on a secondary energy deposit: this will and can only come 
when this secondary will be tracked.

     I hope these explanations will help you to reconsider how to 
organize your sensitive detector code. Also, for further help, you may 
provide a bit more information on your setup.


On 04/09/2013 12:34 PM, Annette Pressman wrote:
> *** Discussion title: Event and Track Management
> I've been looking at alternatives to making the detector sensitive and
> would like to check - it seems that secondary particles are G4Track
> objects. Does this mean that I cannot get the TotalEnergyDepost G4Step
> information about the secondaries in the way I can for the primaries? I
> am very much a novice programmer and really want to find out if I'm
> going down a dead end or not. Thanks for your help. Annette
> On Mon, 01 Apr 2013 20:45:40 GMT, Annette Pressman wrote:
>> Hi, I'm trying to make an absorber sensitive to synchrotron radiation
>> from an electron beam to obtain the deposited energy. I've tried
>> emulating examples B2 and B4d from the basic examples but in both
>> versions of my code I get a segmentation violation at
>> SensitiveDetector::ProcessHits(G4Step*, G4TouchableHistory*)() (in the
>> B2 version) and at G4PSEnergyDeposit::ProcessHits(G4Step*,
>> G4TouchableHistory*)() in the B4d version. I feel I must be missing
>> something, probably quite simple, could anyone point me in the right
>> direction? Many thanks! Annette
> -------------------------------------------------------------
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1 None: Re: Sensitive detector to secondary particles   (Annette Pressman - 09 Apr, 2013)
(_ None: Re: Sensitive detector to secondary particles   (Marc Verderi - 09 Apr, 2013)
(_ None: Re: Sensitive detector to secondary particles   (Annette Pressman - 09 Apr, 2013)
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