[Gate-users] septa penetration

[Chen, Yu]

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?). 


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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