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Question Particle Range Calculation Question 

Keywords: exgps, TestEm1, GPS vs ParticleGun, Positron Range Calculation, Point Source
Forum: Event and Track Management
Date: 02 Jul, 2007
From: Matthew Middione <middionematt@csufresno.edu>

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  

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1 None: Re: Particle Range Calculation Question   (Vladimir IVANTCHENKO - 03 Jul, 2007)
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