<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7638.1"> <TITLE>RE: [Gate-users] Re: Gate-users Digest, Vol 5, Issue 9</TITLE> </HEAD> <BODY>  Hi, Jan and Gaters, Thanks for putting me to think hard about this step issue. First, I would correct what I call interaction range cut before should really mean a user defined step size cut. Range cut is called as production threshold cut for secondaries. In principle, "Transport" process implemanted in Geant4 can deal with: 1) particles crossing boundary; 2) charged particles in a field; 3) particle transportation in the same volume *IF* all other interaction lengths    calculated from other physical processes are longer than user defined max allowed    step size through G4UserLimits method. This actually is a forced step with only    location and no mementum change, labelled as "Transportation" process. However, since the default max allowed step size is DBL_MAX and no field involved in GATE application, we may safely consider the tranportation process is only associated with the change of volume. Hope it is clear this time. 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: gate-users-bounces@lists.healthgrid.org on behalf of D.J. van der Laan Sent: Fri 10/13/2006 1:57 PM To: gate-users@lists.healthgrid.org Subject: Re: [Gate-users] Re: Gate-users Digest, Vol 5, Issue 9 I do not think I completely understand what you mean. As far as I know Geant4 does not limit the step size. The latest release has added this, I think, but only for the multiple scattering processes, so I think this will show up as a multiple scattering and not transport. But perhaps we are talking about two different things. I have used this trick in Geant4 to calculate fluencies through a surface, and I have not noticed any transportation processes except on volume boundaries. The Gate hits file only has the volume id's of the volume in which the interaction occurs, I do not know if this is the post or pre step point.    So it is not possible to use this to detect 'real' boundary crossings. Of course, it is possible to check if the interaction position is on the surface of the volume. Regards, Jan Chen, Yu wrote: > > > I do not think "Transportation" process is only for the purpose > of transporting between different volumes for particles. > > Actually, a hit is a step in Geant4. When a particle travels more than > a interaction range cut (defined as cut threshold) and if there is not > a interaction (processes as compton, photoelectric etc) happened for this > particle, then this step (hit) will be labled as "Transportation" process. > > More accurate way to look for particles crossing a boundary is to find that > step associated with prepoint in pre-volume and postpoint in post-volume. > > Does GATE hit class have those volume names written out? > > Please correct me if I am wrong and misleading. > > 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 > > -- D.J. van der Laan Delft University of Technology Mekelweg 15, room 2.00.020 2629 JB Delft The Netherlands E: d.j.vanderlaan@tnw.tudelft.nl T: +31 15 2783776 F: +31 15 2789011 _______________________________________________ Gate-users mailing list Gate-users@lists.healthgrid.org <A HREF="http://lists.healthgrid.org/mailman/listinfo/gate-users">http://lists.healthgrid.org/mailman/listinfo/gate-users</A> </BODY> </HTML>