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Forum: Space Applications
Re: Question Isotropic flux with Planetocosmics: GPS comands not working properly (Michael Milde)
Date: 12 Jul, 2016
From: Svetlana Shasharina <Svetlana Shasharina>

Hi Michael,
I used similar commands many times and they worked for me.  Are you sure 
you placed Earth in the same center?
Best regards,
Sveta

On 7/12/16 4:36 AM, Michael Milde wrote:
>
> *** Discussion title: Space Applications
>
> Hello everyone,
>
> I need to generate an isotropic particle flux on Earth´s surface through
> the Planetocosmics framework. For the source geometry I use the
> following Geant4 /gps commands:
>
> /gps/pos/type Surface
>
> /gps/pos/shape Sphere
>
> /gps/pos/centre 0. 0. 0. km
>
> /gps/pos/radius 7870 km
>
> /gps/ang/type cos
>
> /gps/ang/mintheta 0.00 deg
>
> /gps/ang/maxtheta 90.00 deg
>
> The expected flux from the starting positions on the source sphere, as
> I´ve read in many threads here, should have a cos modulation centred
> around the perpendicular direction at the source sphere (and thus
> directed to the Earth's centre, since my source sphere is centred in 0 0
> 0 in a planetocentric coordinate frame).
>
> Now my problem: if I run the simulation, the particles are correctly
> generated from the source sphere centred around the Earth, but their
> direction is centred towards a point somewhere in space, and not at the
> Earth's centre, as I would like. In the attachments you can find
> pictures (1-2) of the tracks. In picture 3 and 4 you can see the result
> if I set /gps/ang/mintheta 0.00 deg and /gps/ang/maxtheta 0.00 deg, so
> just the (expected) "zenith" direction is allowed. Here, all the tracks
> are pointed towards some point in space.
>
> I already tried to add commands like /gps/ang/surfnorm,
> /gps/ang/user_coor, but nothing seems to help. Also the circle source
> has the same behaviour.
>
> Did someone encounter this or a similar problem already and was able to
> solve it? Do you have some advices?
>
> Thanks! Best Regards,
>
> Michael
>
>    Attachment:
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/07/12/03.34-42312-PCSimulationSphere1.png
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/07/12/03.34-7371-PCSimulationSphere2.png
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/07/12/03.34-56069-PCSimulationSphere3.png
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/07/12/03.34-7442-PCSimulationSphere4.png
>
> -------------------------------------------------------------
> Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or unsubscribe) at:
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1 Question: Re: Isotropic flux with Planetocosmics: GPS comands not working properly   (Michael Milde - 12 Jul, 2016)
(_ None: Re: Isotropic flux with Planetocosmics: GPS comands not working properly   (sveta - 12 Jul, 2016)
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