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Feedback Re: Wavelength range of material properties and number of Cerenkov photons 

Keywords: Cernkov photons wavelength
Forum: Processes Involving Optical Photons
Date: 05 Mar, 2007
From: Gumplinger Peter <Gumplinger Peter>

Hello Weili,

> In the User Manual, optical photon is defined as photons wich
> wavelength is start from 10nm.

Hmmm, I wasn't aware that such a statement is made anywhere; where?

Optical photons are defined in the range of wavelengths you define; simple as that! In fact, I know of several applications which use the processes defined for 'optical photons' in the X-ray wavelength regime.

> then these UV photons will be shifted to the photons which
> is sensitive to the detector by the process of absorption and
> re-emission of scintillator.

So, you are using the OpWLS process - not the Scintillation process?

> Therefore, I'm confused that what is the proper wavelength range or
> photon momentum range for the physical situation?

The proper wavelength for you to use is the upper and lower limit of wavelength that can be detected in your detector after being shifted. Your WLS has an absorption spectrum that will go to zero. This is the range of Cerenkov photons you need to generate in the radiator. You you also need to propagate these and the resulting WLS photons, assuming your radiator is also the WLS material. So, the range is extended by the WLS emission spectrum. Finally, your detector has a quantum efficiency in a certain WL range. Thus, only the emission spectrum inside that range needs to be modeled.

> The simulation results of including Cerenkov, Scintillation and
> absorption-reemisson which start from 10nm and 200nm are different very
> much.


> So, if I enlarge the wavelength range of material properties and give
> the corresponding refractive indices, geant4 will produce more
> Cerenkov photons

This is true, but the number of detected (detectable) photons in your detector should not change.

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