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Forum: Processes Involving Optical Photons
Re: Question trouble with optical properties meaning
Re: Feedback Re: trouble with optical properties meaning (Gumplinger Peter)
Re: Question Re: trouble with optical properties meaning
Date: 29 May, 2012
From: Vlasios Vasileiou <Vlasios Vasileiou>

Hi Esther,

I wrote the first version of the code to simulate small-angle scattering for the Milagro simulation. There, we had few measurements on the fraction of scattering at different very-forward (~0deg) and very-backward (~180deg) angles. From those measurements, I made up some guesstimates of the forward-backward asymmetry (fraction of ~0deg and ~180deg scatterings that happen at ~0degs), and from the shape of the scattering-angle distribution I figured out some values for g_f and g_b that reproduced our few measurements. Helpful in those calculations was MiePlot (http://www.philiplaven.com/mieplot.htm) and the fact that g_f and g_b are the average cosines of the scattering angles (Note: for backward scattering subtract 180deg from the scattering angle). In Milagro simulation we had g_f and g_b set at 0.999 (i.e., only a slight deviation from an 0 or 180deg scattering angle) and the asymmetry at 0.90 (i.e., mostly forward).

Here is an email sent privately by Xin Qian (xqian caltech edu) to Peter and me:

The way I do it is the following:
    1. figure out the property of the material.
    2. go to the web calculation to get the Mie scattering distribution (also probably strength)
    http://omlc.ogi.edu/calc/mie_calc.html
    3. Fit the distribution with the approximation H-G (then the parameters coming out the fit are those parameters)
    4. Put it into GEANT.


Hope this helps,
Vlasios

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1 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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