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Forum: Event and Track Management
Re: Question How should I slice up a volume to tabulate charge deposition? (Mark Looper)
Date: 17 Jun, 2008
From: Makoto Asai <Makoto Asai>

Hi Mark,

 With the command-based scoring feature in Geant4 version 9.1,
you don't need to implement any extra geometry for scoring.
All you need is the real material volumes. Then, just utilize the
UI commands to define the scoring mesh and the quantities you
want to score.
 Please try examples/extended/runAndEvent/RE03

Makoto

> -----Original Message-----
> From: Mark Looper [mailto:mark.d.looper@aero.org] 
> Sent: Tuesday, June 17, 2008 2:12 PM
> To: eventtrackmanage-g4hn
> Subject: How should I slice up a volume to tabulate charge deposition?
> 
> 
> *** Discussion title: Event and Track Management
> 
> I've been using EGSnrc (and formerly EGS4) to simulate the way that
> spacecraft insulators build up a charge in the energetic-electron
> environment of Earth orbit. I need depth profiles of the charge
> deposition with fairly fine resolution (e.g., many slices through the
> thickness of a circuit board), and EGSnrc has tracking problems with
> very small geometrical sizes, so I'm looking to port my simulations to
> Geant4. However, I'm not sure as to the best way to slice and dice my
> simulation volume to tabulate the distribution of charge deposition.
> 
> In searching these forums, I found a question 
> (http://hypernews.slac.stanford.edu/HyperNews/geant4/get/event
> trackmanage/651.html)
> from a year ago about a similar problem for energy deposit. The
> questioner was defining one geometric volume per histogram 
> bin, and the
> answerers suggested that he should use geometric volumes only 
> for actual
> physical pieces of the geometry and instead tabulate the 
> energy deposit
> on the fly, apportioning each step's continuous energy deposit to the
> bins crossed by that step. To avoid the tracking problems I mentioned
> above for EGSnrc, I have already been doing that for charge deposit;
> however, since charge deposit is a discrete process, I have to track
> down each kind of physical interaction that can cause it 
> (ejection of a
> delta ray, stopping of a charged particle, Compton 
> scattering, ...) and
> set a trap for each. I'm not a sophisticated-enough user of 
> Geant4 to be
> confident that I could manage to do this in Geant4, though!
> 
> The primitive-scorer classes G4PSCellCharge and 
> G4PSCellCharge3D appear
> to return to the model of one geometric volume per histogram bin: you
> assign a scorer to a volume, and it counts the difference between the
> charge of the particles entering the volume and that of the particles
> leaving it, allowing the details of how charge is liberated 
> or captured
> to stay hidden inside the volume. My question amounts to "am I missing
> something here?" At the energies of interest to me, I wouldn't be
> wasting a lot of extra processing time unnecessarily interrupting the
> flight of gammas at region boundaries, so there'd be little benefit to
> my learning how to set a physical-volumes-only geometry for 
> gammas and a
> sliced-and-diced geometry for charged particles. However, is 
> there some
> way that I could instead replicate my EGSnrc procedure (and 
> that of the
> answers to the question I mentioned above), getting hold of the actual
> charge-deposition events and localizing them to individual bins? This
> would avoid a lot of time wasted by interrupting the tracking on
> artificial "bin" region boundaries just to cancel out the 
> entry and exit
> of all the particles that don't cause charge-deposition events in a
> given bin.
> 
> Many thanks!
> -------------------------------------------------------------
> Visit this GEANT4 at hypernews.slac.stanford.edu message (to 
> reply or unsubscribe) at: 
> http://hypernews.slac.stanford.edu/HyperNews/geant4/get/eventt
> rackmanage/823.html 
> 

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1 None: Re: RE: How should I slice up a volume to tabulate charge deposition?   (Mark Looper - 19 Jun, 2008)
(_ Ok: Re: RE: How should I slice up a volume to tabulate charge deposition?   (Mark Looper - 10 Sep, 2008)
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