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Forum: Processes Involving Optical Photons
Re: Question Material Properties Table (Eric)
Date: 30 Nov, 2010
From: Gumplinger Peter <Gumplinger Peter>

Hi Eric

> I guess my question is: Is anything significant about 32?

No!

> How would the behavior change if instead
> of using 32 entries, I used the first and last entries, giving me 2?

The property vector is linearly interpolated between the energy values you give. So it depends on how much the property-change deviates from this linearity, how many values you should provided to get a 'good enough approximation'.

> Also, the photon energies range from 2.034 eV to 4.136 eV... how does
> this table give the material information for instance, if a photon of
> energy 100 eV interacts with it?

It will write a warning and give you the value of the largest bin. Similarly, it will give you the smallest bin for e < emin.

> 
> Any other general information about how this table is accessed and used
> would be greatly appreciated.

The is a paragraph in the Application Developers Manual near the top of:

http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch05s02.html#sect.PhysProc.Photo

G4 calls the table for every optical photon it is tracking to extract the property. If it is tracking a photon with an energy between bins then there needs to be an interpolation. If you only ever track photons of one and the same energy, all you need it two bins slightly on each side of that energy. For a constant property you also only need two bins.

Peter

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