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

Many thanks for your help Marc, that has made all the difference. Its working!! Woot! You've made me very happy, have a great day!

Cheers, Annette

On Tue, 09 Apr 2013 12:34:09 GMT, Marc Verderi wrote:

> So I understand that your setup is such that your fan only receives 
> contribution from the synchrotron radiation photons. Is that correct ? 
> In this case, you only need to accumulate in your fan all deposited 
> energies, regardless of the particles which deposits it. And that's all.
> 
> You indeed noticed that photons almost never deposit energy, and this is 
> correct: photons do not deposit energy by themselves, directly: these 
> are the electrons/positrons, created by these photons which are doing 
> so. So, if your fan is only hit by these sync rad photons, all 
> subsequent energy deposits are all due to daughters, grand-daughters, 
> grand-grand-daughters, etc. of these initial sync photons.
> 
> Hope this helps.
> 
> Cheers,
> Marc
> 
> On 04/09/2013 01:33 PM, Annette Pressman wrote:
> > *** Discussion title: Event and Track Management
> >
> > Dear Marc,
> >
> > Thank you, that helps! I'm trying to simulate a synchrotron radiation
> > 'fan' from an electron beam being curved into an interaction region, so
> > that I can model absorbers for the fan. The synch radiation model is
> > based on TestEm15 with gamma energies and steplengths obtained in
> > SteppingAction. I am interested to know how much energy will be
> > deposited in the absorber and beampipe from this secondary radiation.
> >
> > Most of the secondary gamma rays do not, and never will, interact with
> > my absorber or the surrounding beampipe. I think this is why I am
> > struggling to make my absorber and beampipe 'sensitive' - that
> > ProcessHits isn't being initiated for most particles?
> >
> > As an alternative to the sensitive detector I have tried to obtain the
> > deposited energy from SteppingAction directly using the following code,
> > or variations on this theme (based on analysis example AnaEx02).
> >
> > G4Track* theTrack = aStep->GetTrack();
> >
> > G4VPhysicalVolume* volume =
> > aStep->GetPreStepPoint()->GetTouchableHandle()->GetVolume();
> >
> > if (aStep->GetTrack()->GetDefinition()->GetPDGCharge() == 0.){
> >      G4double edep = aStep->GetTotalEnergyDeposit();
> >      G4double stepl = 0.;
> >      stepl = aStep->GetStepLength();
> >
> >      if (volume == fDetector->GetPipe())      fEventAction->AddPipe    (edep,stepl);
> > }
> >
> > However no matter how I alter this to fill only with the (secondary) SR
> > photons I only ever obtain deposited energy for the primary electrons -
> > which is zero. However from what you say, I guess the secondaries will
> > each be processed eventually by G4Step so the deposited energy should be
> > available?
> >
> > Thanks again for your help! Annette
> >
> > On Tue, 09 Apr 2013 11:01:15 GMT, Marc Verderi wrote:
> >
> >> 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.
> >>
> >> Cheers,
> >> Marc
> >>
> >> 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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