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Question Isotropic flux with Planetocosmics: GPS comands not working properly  

Forum: Space Applications
Date: 12 Jul, 2016
From: Michael Milde <Michael Milde>

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

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1 None: Re: Isotropic flux with Planetocosmics: GPS comands not working properly   (sveta - 12 Jul, 2016)
(_ 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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