Problem 585

Summary: Penelope has fleas! (at least, G4PenelopeCompton has bugs)
Product: Geant4 Reporter: marcus.h.mendenhall
Component: processes/electromagnetic/lowenergyAssignee: Luciano Pandola <luciano.pandola>
Status: RESOLVED FIXED    
Severity: major    
Priority: P2    
Version: other   
Hardware: All   
OS: All   
URL: http://arago.fel.vanderbilt.edu/~marcus/

Description marcus.h.mendenhall 2004-02-18 09:49:36 CET 
I have been running a code to simulate energy deposition by xrays in the 50 keV - 10 MeV energy
range for a medical physics problem.  Up until now, I have always run the beam in along the z-axis.
Yesterday, I introduced variable direction beams (so I could sum over multiple doses) and got a
surprise.  The energy deposition around beams not running along te z-axis is very asymmetrical with
the +z axis being preferred to the -z axis in G4PenelopeCompton events.  Changing
G4PenelopeCompton to G4LowEnergyCompton produces the expected result with the energy deposition
symmetrical about the beam axis.

I have posted images of the energy deposition for each case at the URL listed below. The files of
interest are image_lowenergy.jpg and image_penelope.jpg.  The problem is immediately visible in the
Penelope image.

 I will try to start poking around PenelopeCompton for this, but someone who is really familiar with the
Penelope physics package might have a better shot at finding it quickly.
Comment 1 Gabriele Cosmo 2004-02-19 05:41:59 CET 
*** This bug has been marked as a duplicate of 584 ***
*** 'Maria.Grazia.Pia@cern.ch' will be responsible for this bug. ***
Comment 2 Maria.Grazia.Pia 2004-02-20 05:57:59 CET 
This problem report is the correct one, not Problem Report 584.
Comment 3 Maria.Grazia.Pia 2004-02-24 06:45:59 CET 
The problem is reassigned to the Geant4 developer responsible for Penelope
processes.

Best wishes,
Maria Grazia Pia
Comment 4 Luciano Pandola 2004-03-09 04:53:59 CET 
Thank you for your report. A problem was found with the reference system in the
final state. A corrected version of the code will be available in next Geant4
public release.