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Forum: Event and Track Management
Date: 24 Jul, 2009
From: Greg Damhorst <Greg Damhorst>

Hello, I'm a new GEANT user and I'm trying to do a very simple simulation of optical photons on a scintillating fiber. To do this, I create optical photons isotropically at the center of a single-clad fiber using G4ParticleGun.

What I found is that somewhere between the 20th and 30th photon in a run of 100, I hit a "sweet-spot" momentum direction where my photon bounces around inside the fiber and never leaves (thus the program continues to calculate millions of steps for a single photon and, as far as I can tell, will never stop).

I'd like to kill a photon like this (say, after a certain number of steps) so my program can move on and calculate the next photon trajectory. Any ideas on the simplest way to do this?

I've tried G4UserLimits and G4UserSpecialCuts in DetectorConstruction and PhysicsList, respectively, as an example I found seemed to describe. However, this compiles successfully and then can't run (I get errors telling me I need to construct electrons!), so if you suggest these methods please be very specific about what I need.

I've also tried to set an absorption length in the fiber material, but when I do this the application ignores the boundary process/refractive indexes I've set and just shoots photons straight through my material.

Any insight is certainly appreciated.

Greg Damhorst

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1 Disagree: Re: Killing Photons   (Gumplinger Peter - 24 Jul, 2009)
(_ None: Re: Killing Photons   (Greg Damhorst - 25 Jul, 2009)
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