[Gate-users] septa penetration

[Simon Stute]

Hi all,


On Fri, Mar 5, 2010 at 10:36 PM, Chen, Yu <Yu.Chen at umassmed.edu> wrote:

> We are using the method Simon mentioned to deal with completely absorption
> cases.
>
> We use Uranium (Z=92?) and density=10000(?) to successfully stop all
> particles in the material. I checked root file to see the ranges are all
> within micrometers.
>
>
I do not know if there is a problem with arbitrary high Z number (Geant4 may
> have a limitation on effective Z?).
>


And yes ... there is a limitation ... I tested it and G4 limits by an
"assert" Z to 101, but it gave me segmentation violation above 98. So the
limit is Z=98 !
And even by removing the assert, segmentation violation are also obtained
above Z=98.

Thanks Yu :-) for the estimation of the range.
Cheers,
Simon


>
>
> Yu Chen, PhD
> Walter Reed Army Medical Center
> Building 2, Room 1H46A
> 6900 Georgia Avenue, NW
> Washington, DC 20307
> Phone: (202) 782-1881
> Fax: (202) 782-0305
> E-mail: yu.chen1 at us.army.mil
>
>
> Date: Fri, 5 Mar 2010 11:22:30 +0100
> From: Simon Stute <gate.stute at gmail.com>
> Subject: Re: [Gate-users] septa penetration
> To: Cl?udia R?gio Brambilla <claudinha.rb at gmail.com>
> Cc: gate-users at lists.opengatecollaboration.org
> Message-ID:
>        <38e368331003050222i4de1dba1n372cfa6659834217 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hi,
>
> 2010/3/4 Cl?udia R?gio Brambilla <claudinha.rb at gmail.com>
>
> > Hi gate users,
> >
> >
> >
> > I have two questions:
> >
> >
> >
> >
> >
> > 1-      Does anybody knows if gate 5 or 6 could simulate septa
> penetration?
> >
>
> Of course, Gate is a Monte Carlo tool !
> But to know it I think you have to put a point source of gamma (with the
> energy of your choice) in the center of a Lead cube and then calculate the
> mean distance between the point source and the position of final
> interaction
> of your gammas.
>
>
> > Or Are the events absorbed when it hits in a Pb material collimator?
> >
>
> No of course, why it should ?
>
>
> >
> > 2-      Is it possible to introduce any command to force absorb event
> when
> > it hits on shielding to reduce the time of the simulation?
> >
> >
> >
>
> I am also thinking about that now and considering my very little
> understanding of physics around particle transport in matter, I think we
> can
> approach this by defining a new element with a very high Z and a new
> material made of this element with a very high density. As photoelectric
> usually depends on Z^4 and compton only on Z, by setting a very high Z you
> maximize the probability of photoelectric much larger than for compton. But
> I havn't tested it yet !
> And if anybody more experienced in this domain can correct or confirm this,
> it would be great !
>
> But if you use Gate_v6 there is also  the possibility to easily assign a
> very high cut for gamma in your collimator volume, it is much more
> convenient !
>
> Cheers,
> Simon
>
>
> >
> > Thanks for help,
> >
> >
> >
> > regards
> >
> > __________________________________
> >
> >
> >
> > Cl?udia R?gio Brambilla
> >
> >
> >
> > _______________________________________________
> > Gate-users mailing list
> > Gate-users at lists.opengatecollaboration.org
> > http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
> >
>
>
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