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Question trouble with optical properties meaning 

Forum: Processes Involving Optical Photons
Date: 19 May, 2012
From: <esther>

Hi,

I'm simulating cerenkov effect in water starting from example N06, and I have some trouble in understanding the meaning of the optical parameters that have to be defined in the material properties tables.

I have no problem with the absorption length ABSLENGTH, I even compared the values given in the example's DetectorConstruction class with those measured and reported in literature and they agree very well.

My first problem is the dependence on energy of the index of refraction: I tried to use a few formulas reported for example in "Bashkatov, Water refractive index in dependence on temperature and wavelength: a simple approximation", but I get totally different results from those in exampleN06. Can anyone tell me where those numbers come from?

Then there is rayleigh scattering length, which is calculated, I suppose, using Einstein-Smoluchowski formula, that expresses a relation between diffusion coefficient and temperature, therefore to get the scattering coefficient we use:

D = 1/(mu'_s + mu_a)

where mu_a is the inverse of the abs length previously discussed, and mu'_s = (1 - g)mu_s, right?

So what do I get from Einstein-Smoluchowski; mu_'s or mu_s? Or am I completely wrong?

The last parameters are related to Heyney-Greestein approximation of Mie scattering: I couldn't find any publication for Mie scattering length, and I really don't get the meaning of the three parameters MIEHG_FORWARD, MIEHG_BACKWARD, and MIE_FORWARD_RATIO. I know they are the parameters which enter in formula (13.5) of the Physics reference manual, relative to the final differential cross section for Mie Scattering, but still can't get their meaning. I mean: isn't any material characterized just by ONE anisotropy factor, that tells about any preferential direction of emission? Then, what are g_f and g_b?

It's important to me to understand how to get these tables, because later I'll have to replace water with other materials, so tables in exampleN06 won't no longer be useful.

Thanks to anyone who answers,

Esther.

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1 Feedback: Re: trouble with optical properties meaning   (Gumplinger Peter - 22 May, 2012)
(_ Question: Re: trouble with optical properties meaning   (esther - 24 May, 2012)
(_ None: Re: trouble with optical properties meaning   (Vlasios Vasileiou - 29 May, 2012)
(_ Question: Re: trouble with optical properties meaning   (esther - 07 Jun, 2012)
(_ Feedback: Re: trouble with optical properties meaning   (Gumplinger Peter - 07 Jun, 2012)
(_ Ok: Re: trouble with optical properties meaning   (esther - 08 Jun, 2012)
(_ Question: Re: trouble with optical properties meaning   (Aram Teymurazyan - 04 Feb, 2013)
(_ None: Re: trouble with optical properties meaning   (Vlasios Vasileiou - 06 Feb, 2013)
(_ None: Re: trouble with optical properties meaning   (Aram Teymurazyan - 06 Feb, 2013)
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