Problem 845

Hello,

I am trying to run GEANT4 simulations where I would like to construct a
radioactive sample to model a beta-decay. As a sample of the code I have used
"exrdm" example. I have a few questions about this example. First of all, in the
top of the file called "exrdm.out" one could see the usual output of the GEANT4.
Namely, one could see the tag of the GEANT4's version with the day when this
version was released. For the mentioned example the tag corresponds to the
latest version of the GEANT4 (geant4-08-00-pathch-01), however the release day
corresponds to the 27-July-2004. Therefore, I would like to know was this
example compiled and run with the latest GEANT4 code and with the latest data
library.

Secondly, I have found a part of the code (file called exrdmSteppingAction.cc)
that I do not understand properly. This is a part where initial conditions of
the particle that have been created during radioactive decay are stored. The
initial information (particle name, energy, weight and time) is stored for any
particle that is not a nucleus. If someone would like to simulate a beta-decay
with GEANT4 one of the particles that would be created by Radioactive Decay
process is neutrino, and neutrino is not a nucleus, and its initial information
is stored as well. That could create a problem if one is interested in the
emission spectra from radioactive nuclei that would be consisting i.e. from beta
and gamma particles. For example, if we can choose decay of Co60 in the initial
spectra that would be created by exrdm program we will not find a characteristic
shape of the beta-spectra.

Thirdly, if in the command file called "exrdm.in" in the top of the file as an
additional command I will add line "/control/saveHistory" as an output from
GEANT4 I will get a file called G4History.macro. This file contains records of
all commands that were sent to GEANT4. I am confused with the next line:
/gps/pos/center 0. 0. -25
This line does not contain a dimension of the length for the center position,
which seems a little bit suspicious. Originally in the code (file called
exrdmDetectorConstruction.cc) general purpose source is set to the center of the
World, which is half of the detector length (fDetectorLength = 5.0 * cm). So, I
would expect that when I simulate 1GeV proton beam on the NaI target (exrdm.in
example) I should see an initial Z-position of the proton from the track
information to be -25 mm. Nevertheless, the output from GEANT4 shows center of
the source as -250 mm.

I am not an expert in GEANT4 and I would be appreciated any help from GEANT
community.
Regards,
Victor Golovko.
February 23, 2006