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Forum: Processes Involving Optical Photons
Re: Sad Optical photon as primary particle/Length absorption problem (Clément DUPONT)
Date: 20 Jan, 2015
From: Michael H. Kelsey <Michael H. Kelsey>

One observation and one question for you:

On Tue, 20 Jan 2015 16:40:03 GMT, Cl&#65533;ment DUPONT wrote:

> I try to simulate absorption and scattering process of visible photon
> (wavelength about 630 nm, equal to 1,96 eV) in the "G4 world" composed
> of water (I begin with a very simple simulation).
> I mainly took inspiration from the example "novice 6".
> The only problem I have is that my photons are absorbed after a
> propagation of only a few micrometers which is not correct. I don't know
> where can be situated my mistake.
> I declare my water properties as in the example novice 6.
> 
> G4double photonEnergy[] =
>     { 2.034*eV, 2.068*eV, 2.103*eV, 2.139*eV,
>         2.177*eV, 2.216*eV, 2.256*eV, 2.298*eV,
>         2.341*eV, 2.386*eV, 2.433*eV, 2.481*eV,
>         2.532*eV, 2.585*eV, 2.640*eV, 2.697*eV,
>         2.757*eV, 2.820*eV, 2.885*eV, 2.954*eV,
>         3.026*eV, 3.102*eV, 3.181*eV, 3.265*eV,
>         3.353*eV, 3.446*eV, 3.545*eV, 3.649*eV,
>         3.760*eV, 3.877*eV, 4.002*eV, 4.136*eV };

Your energy range is above the energy of your primaries. You are doing a spline, so there should be a sensible extrapolation below 2.034, but I don't like to assume that. If you have absorption data below 1.96 eV, you should try to extend your photonEnergy[], rIndex[] and absorption[] arrays.

My other question is how do you create your primaries? If you're using the /gun/particle macro command, are you specifying "opticalphoton" or just plain "photon." The two are not (as I've learned the hard way) interchangeable.

     -- Michael Kelsey

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1 Note: Re: Optical photon as primary particle/Length absorption problem   (Clément DUPONT - 20 Jan, 2015)
(_ Feedback: Re: Optical photon as primary particle/Length absorption problem   (Gumplinger Peter - 20 Jan, 2015)
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2 Ok: Re: Optical photon as primary particle/Length absorption problem   (Clément DUPONT - 21 Jan, 2015)
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