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Agree Re: Energy deposited is larger than the energy of the primary gamma beam 

Forum: Processes Involving Optical Photons
Re: Question Energy deposited is larger than the energy of the primary gamma beam (Martin Kocan)
Re: Feedback Re: Energy deposited is larger than the energy of the primary gamma beam (Gumplinger Peter)
Re: None Re: Energy deposited is larger than the energy of the primary gamma beam (Martin Kocan)
Date: 31 Jan, 2014
From: Gumplinger Peter <Gumplinger Peter>

Hi Martin,

The generation of optical photons does NOT conserve energy. This is explained in the manual. Therefore, you MUST NOT add the energy lost by an optical photon - however small - to your energy tally of the NaI. The simplest way to avoid this is by disallowing any and all optical photons from contributing to your energy tally logic regardless of where the steps are in your geometry. After that you should find perfect energy conservation. The energy (wavelength) of the optical photons shall be used only in connection with their optical properties.

> 2. Regarding the necessity of refractive index definition for AlHousing,
> my understanding was to define this physical quantity for both materials
> that form a boundary interface described via G4LogicalBorderSurface.

The index of refraction is only required for material in which you expect optical photons to propagate any finite distance; e.g. dielectric material. If you define your G4LogicalBorderSurface to be of type dielectric_metal then you don't have to provide the (complex) index of refraction of the 'metal' - unless you want the program to calculate the reflectivity from the metal's complex index of refraction. In most cases, users will simply provide an empirical reflectivity.

> 3. Regarding the reflectivity of 94% for NaI internal walls instead of
> 100%: since we don't know what the reflector in a real NaI scintillator
> is made of, the value of 94% seems to show the best agreement with
> spectral measurement.

Sure, but that's why you are 'detecting' fewer photons than are generated.

Peter

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