[gate-users] Photons ID's from decay sources

[Schmidtlein, Ross/Sloan-Kettering Institute]

Hi Dirk and Dimitris,

I figure you both are the most likely to know the answer to this
question but if anyone else knows please speak up ;).  

I have been looking at the root output for Hits, Singles, and
Coincidences and am trying to determine the source particle's identity
be it positron or cascade photon?  Inside the Hit's Branch I am looking
into ParentID, PhotonID, and PrimaryID.  So far ParentID looks the most
likely but I don't know how to interpret this.

Thanks,

ross

-----Original Message-----
From: gate-users-bounces at lphe1pet1.epfl.ch
[mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of Dirk Kruecker
Sent: Tuesday, June 14, 2005 5:52 AM
To: GATE feedback and helpline for Users
Subject: Re: [gate-users] source of germanium68


Hello everybody,

Let me summarise the present status on the beta decay module in GEANT4:

There is a beta decay module in GEANT4 that works quiet nice. It allows
you to 
simulate the decay of all kinds of nuclei using the ENSDF 
(http://www.nndc.bnl.gov/ensdf/).
It simulates any possible decay, taking into account the latest
knowledge on 
branching ratios and creates all possible gammas from the de-excitation
of 
the daughter-nucleus.
So you get the right ratio between beta+ and EC, and for each possible
decay 
channel the appropriate gamma spectrum in coincidence with the positron.

In GATE the commands to implement e.g. Y86 looks like:  
/gate/source/addSource ytt86
/gate/source/ytt86/setActivity 500000000. becquerel
/gate/source/ytt86/gps/particle ion /gate/source/ytt86/gps/ion 39 86 0 0
/gate/source/ytt86/gps/energytype Mono /gate/source/ytt86/gps/monoenergy
0. MeV /gate/source/ytt86/gps/angtype iso /gate/source/ytt86/gps/number
1 /gate/source/ytt86/gps/centre 0. 0. 0. cm /gate/source/ytt86/gps/type
Volume /gate/source/ytt86/gps/shape Sphere /gate/source/ytt86/gps/radius
0.1 mm
/gate/source/ytt86/gps/mintheta    0. deg
/gate/source/ytt86/gps/maxtheta  180. deg
/gate/source/ytt86/gps/minphi      0. deg
/gate/source/ytt86/gps/maxphi    360. deg

The important part here is the /gate/source/ytt86/gps/ion 39 86 0 0
command where Z and A are defined. You can define all kinds of isotops
here.

Unfortunately there had been several bugs in the GEANT4 code for the
beta 
decay and even the latest version  does not run absolutely stable. In 
addition the original implementation is astonishing inefficient (i.e.
slow) 
but there is a fast mode sufficient for our purposes.

For GEANT4 version 4.52-4.62 you need patches in
GateRadioactiveDecay5.cc and G4NuclearDecayChannel.cc which I can
provide but I would rather use gate 
1.2 with GEANT 4.7. For this version of GEANT I have provided an
improved 
algorithm for simulating the beta energy spectra. 

To my knowledge the version GEANT 4.7 will give you correct physical
results 
but it still contains some bugs which affect the stability of the
program. 
There are at least 2 memory leaks. One I already fixed
http://geant4.cern.ch/asdcgi/geant4/problemreport/show_bug.cgi?id=711
but this is not yet part of any GEANT4 patch. Presently you have to
include it 
by hand.

I am still hunting for the second memory leak. Usually it only show up
after 
simulating several millions of decays. On average my jobs run for 24h/12

million events and about 1 of 8 jobs crashes. If you can live with this
I 
would give it a try.

I hope the helps. Let me know if you really want to work with the older
GEANT4 
version.

Best Regards,
Dirk








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