[gate-users] Re:RE: Re:Re: no e-/e+ tracking!

[Chen, Yu]

Hi, BG and others,

I have to clarify some misunderstanding here:

1) you cannot get rid of secondary e- completely since you
want to simulate photoelectric and compton processes!

2) the amount of secondary photoelctrons and compton scattered 
electrons is dependent on the low limit of energy provided in the 
selected physics models. I rememeber the default low limit in 
low energy EM model (based on many measurement data) is 250eV which
means when gamma energy is lower than this value, no EM (pe, compton etc)
process is allow to be occurred. Currently, GATE does not have a method
to change this value. And in most cases, you do nto need to change it.

3) delta ray is produced by high energy charged particle (>GeV). The chance
to produce delta ray by secondary e- is very very low. I do not see any 
necessarity to implement such deltaray cut since it won't happen.

4) The best we can do now to save some time is setting the electron cut range
as high as possible to let it stop at the first step (one e- one hit).

Hope it is clear this time.

Best, Yu  

Yu Chen, Ph.D.
University of Massachusetts Medical School
Division of Nuclear Medicine
55 Lake Avenue North
Worcester, MA 01655-0243
Phone:  (508) 856-6123
Fax:    (508) 856-4572



-----Original Message-----
From: Bastien Guérin [mailto:guerin at bwh.harvard.edu]
Sent: Wed 8/3/2005 12:10 PM
To: gate-users at lphe1pet1.epfl.ch
Subject: [gate-users] Re:RE: Re:Re: no e-/e+ tracking!
 
Dear all,

M. Chen recently pointed out that the routines:

void GateElectronPhysics::SetDeltaRayCut(G4double val)
void GateGammaPhysics::SetDeltaRayCut(G4double val)

have not been yet implemented in Gate. A large value for the electron cut
can force the knock-out e- to deposit their energy locally but they are
still produced. A correct implementation of the two functions above would
prevent also their production. This would finally remove totally and
rigorously the tracking of e- in Gate.
It seems extremely useful to implement these since it could provide a mode
in Gate "without electrons", which is, according to the gate-users talk
archives, what a lot of people try to do. Does s.o. familiar with the code
already implemented correctly these functions?
 
M. Chen: I made the experiments you suggested. It's definitely important to
chose an intelligent value of the e- cut depending on one's application, the
gain in time and file size can be large. I prefer you write me directly if
you want to discuss that further.

All the best,

BG

----

Bastien Guerin
PhD candidate, University of Paris
Visiting Fellow, Harvard University
work: 617-525-6629
urgent: 617-817-2762


-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/ms-tnef
Size: 4102 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20050804/dc404451/attachment.bin>