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Forum: Event and Track Management
Re: None G4GeneralParticleSource: spherical source radiating inwards?? (Constantin Athanassas)
Re: None Re: G4GeneralParticleSource: spherical source radiating inwards?? (Youming Yang)
Re: None Re: G4GeneralParticleSource: spherical source radiating inwards?? (Constantin Athanassas)
Date: 21 Aug, 2016
From: Constantin Athanassas <Constantin Athanassas>

I think I found the answer:

http://hypernews.slac.stanford.edu/HyperNews/geant4/get/particles/494/2.html

This should be the solution I suppose.

Constantin

On Sun, 21 Aug 2016 10:54:07 GMT, Constantin Athanassas wrote:

> Thanks, Ming. It's working now. However how can I define the theta angle
> so that the rays come only from the half of the sphere (i.e. 2-pi solid
> angle)? Would the following macro syntax help?
> 
> /gps/ang/mintheta 0 rad /gps/ang/maxtheta 1.57 rad # i.e. pi/2.
> 
> Also, when I insert the radius as:
> 
> /gps/radius 6 cm
> 
> I get the following warning:
> 
> "G4GeneralParticleSourceMessenger - Warning: The command is obsolete and
> will be removed soon. Please try to use the new structured commands!"
> What does it mean?
> 
> Thanks in advance. Best, Constantin
> 
> On Sat, 20 Aug 2016 07:26:28 GMT, Youming Yang wrote:
> 
> > Hello,
> > 
> > Perhaps you may want to try 
> >   /ang/type focused
> > rather than
> >   /ang/type cos
> > 
> > you can see what it does in the file 
> >   <G4sourcedir>\source\event\src\G4SPSAngDistribution.cc
> > 
> > in line 301:
> > 
> >  void G4SPSAngDistribution::GenerateFocusedFlux(G4ParticleMomentum& mom)
> >  {  mom = (FocusPoint - posDist->GetParticlePos()).unit();
> >     ...
> >  }
> > 
> > where the particle momentum will basically be set as wherever the
> > particle is, minus the "focus" point (which you can set as origin), so
> > that wherever the particle gets generated, it will point towards the
> > focus point and fly back.
> > 
> > best, Ming
> > 
> > On Fri, 19 Aug 2016 18:42:25 GMT, Constantin Athanassas wrote:
> > 
> > > Hello,
> > > 
> > > I am working on extended example: extended/eventgenerator/exgps. I am
> > > trying to replicate the example macro at the end of the link:
> > > 
> > > https://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch02s07.html#eqn.GPScosine
> > > 
> > > but I want to use a spherical source radiating inwards, towards the SiO2
> > > sphere at the center, not outwards. I am using the following macro:
> > > 
> > > /gps/particle gamma
> > > 
> > > /gps/pos/type Surface
> > > 
> > > /gps/pos/shape Sphere
> > > 
> > > /gps/pos/centre 0 0 0 cm
> > > 
> > > /gps/radius 6 cm
> > > 
> > > /gps/ang/type cos
> > > 
> > > /gps/ene/type Lin
> > > 
> > > /gps/ene/min 2 MeV
> > > 
> > > /gps/ene/max 10 MeV
> > > 
> > > /gps/ene/gradient 1
> > > 
> > > /gps/ene/intercept 1
> > > 
> > > /run/beamOn 100
> > > 
> > > but the flux always seems to be directed outwards, either from the
> > > center of the SiO2 sphere or on the 6-cm-wide shell, depending on the
> > > combination of values assigned to:
> > > 
> > > /gps/ang/mintheta and
> > > 
> > > /gps/ang/maxtheta
> > > 
> > > but never towards the center of the setup, which is the wanted.
> > > 
> > > I followed the steps shown in thread:
> > > http://hypernews.slac.stanford.edu/HyperNews/geant4/get/space_app/79/2/1.html
> > > 
> > > but, still, the model does not cooperate.
> > > 
> > > Can someone help?
> > > 
> > > Thanks in advance,
> > > 
> > > Constantin Athanassas, NTUA.
> > > 
> > 
> 

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