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Forum: Event and Track Management
Re: Question Particle Range Calculation Question (Matthew Middione)
Date: 03 Jul, 2007
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Mon, 2 Jul 2007, Matthew Middione wrote:

> *** Discussion title: Event and Track Management
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/eventtrackmanage/668"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> I have a question regarding the calculation in Geant4 of a particle's range.
> 
> The reason why I ask is because I have merged existing examples within Geant4
> (TestEm1 and exgps).  The reason for the merge is because I wanted to 
> model a point source method to determine positron range from certain
> positron emitting radionuclides.  
> 
> Everything works properly after merging the code, but my results are not
> what I want them to be.  See below:
> 
> Macro File input
> /pr/det/setMat Tissue
> /pr/det/setSize 2 m
> /run/initialize
> /pr/phys/setCuts 1 mm
> /gps/particle ion
> /gps/ion 9 18 0 0 
> /gps/ene/type Mono
> /gps/ene/mono 0.0 MeV
> /grdm/fBeta 1
> /run/beamOn 1
> 
> Results from simulation
> ====================================================================
> 
> ### Run 0 start.
> 
> --------- Ranecu engine status ---------
>  Initial seed (index) = 0
>  Current couple of seeds = 9876, 54321
> ----------------------------------------
> 
> ---> Begin of Event: 0
> 
>  ======================== run summary ======================
> 
>  The run was: 1 F18[0.0] of 1.344 MeV through 2 m   of Tissue (density: 1 g/cm3 )
> 
>  ============================================================
> 
>  total energy deposit: 1.344 MeV
> 
>  nb tracks/event   neutral:          3   charged:         29
>  nb  steps/event   neutral:         27   charged:         58
> 
>  nb of process calls per event:
>    RadioactiveDecay         msc       eIoni     annihil       compt     phot   Transportation
>               2             28          27           1          24       2           1
> 
> ---------------------------------------------------------
>  Primary particle :
>  true Range = 0 fm    rms = 0 fm
>  proj Range = 0 fm    rms = 0 fm
>  proj/true  = nan
>  transverse dispersion at end = 0 fm
>       mass true Range from simulation = 0 mg/cm2
>        from PhysicsTable (csda range) = 0 mg/cm2
> ---------------------------------------------------------
> 
> From the above you can see that I am attempting to model F-18 positrons in tissue like material.
> Thus, I have set the kinetic energy of the F-18 source to 0.0 MeV and enabled fast beta decay.
> 
> This results in range values of 0.0 across the board.  I believe this is due to the fact 
> that the range calculations taking place are being done with the kinetic energy of my source
> as opposed to the energy which is being deposited by the emitted positrons.  From above you
> can see that 1.344 MeV is being deposited from the positrons, but this value is not being 
> incorporated into the range calculations.
> 
> My RunAction.cc which executes the range calculations is unchanged from the example TestEm1.  
> 
> I know something needs to be altered to allow for the range calculations to be executed with 
> the deposited energy as opposed ot the kinetic energy of the source, but I do not know how 
> to go about doing this.  Any help would be much appreciated...
> 
> Thanks in anticipation.
> Matthew Middione  
> 

F-19 is a primary particle. It has zero kinetic energy and zero range.

I would recommend at the beginning to use

/tracking/verbose 1

to control simulation history 
 
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