<html dir="ltr"><head> <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252"> <style id="owaTempEditStyle"></style><style title="owaParaStyle"></style> </head> <body ocsi="x"> <div style="FONT-SIZE: x-small; COLOR: #000000; DIRECTION: ltr; FONT-FAMILY: Tahoma"> <div dir="ltr"> <a></a>Dear Gaters<a></a>, I am<a></a> facing<a></a> an issue I don't<a></a> understand<a></a>, with<a></a> my<a></a> current<a></a> description of my<a></a> setup, it<a></a> seems<a></a> that<a></a> the X rays scattering<a></a> depends<a></a> on the order<a></a> in which<a></a> volumes have been declared<a></a> To mimic<a></a> the CT scan of a composite material<a></a> (I am<a></a> using<a></a> Gate<a></a> to understand<a></a> a CT-Scan setup used<a></a> for Aeronautical<a></a> part testing<a></a>), I am<a></a> introducing<a></a> a periodic<a></a> network of carbon<a></a> fiber<a></a> along<a></a> each<a></a> direction in my<a></a> test phantom<a></a> (Let’s<a></a> call these<a></a> direction 1, 2, 3) If I check the branches ComptVolName<a></a> and RayleighVolName<a></a> in the Hit Tree<a></a>, there<a></a> is<a></a> always<a></a> one direction producing<a></a> more scattering<a></a>. However<a></a>, whatever<a></a> the rotation of the phantom<a></a>, the later-declared<a></a> direction is<a></a> always<a></a> the one producing<a></a> the most<a></a> scattered<a></a> hits. <a></a>Here is<a></a> a pseudo phantom.mac<a></a> /gate<a></a>/world/daughters<a></a>/name<a></a> epoxyBox<a></a> #Define<a></a> an epoxy<a></a> box, /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder1<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder2<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder3<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> All the Carbon<a></a> cylinders<a></a> are copy-pasted<a></a> and I change only<a></a> the rotation along<a></a> X/Y/Z . After<a></a> running the simulation, if I check which<a></a> volumes produces<a></a> the most<a></a> scattered<a></a> hits (from<a></a> Hits/CompVolName<a></a> and Hits/RayleighVolName<a></a>) the volume producing<a></a> the most<a></a> scattered<a></a> hits is<a></a> CCylinder3<a></a> whatever<a></a> the rotation of the epoxyBox<a></a> If now<a></a> I declare<a></a> the CCylinder<a></a> in a different<a></a> order<a></a> i.e<a></a> /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder3<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder1<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> /gate<a></a>/epoxyBox<a></a>/daughters<a></a>/name<a></a> CCylinder2<a></a> #Define<a></a> and rotate<a></a> an array<a></a> of carbon<a></a> Cylinder<a></a> using<a></a> Repeater<a></a> <a></a>Now the CCylinder<a></a> producing<a></a> the most<a></a> scattered<a></a> hits is<a></a> CCylinder<a></a> 2 (whatever<a></a> the rotation of the epoxy<a></a> box) I made all the rotation testing<a></a> with<a></a> few photons (around<a></a> 100 000) to save<a></a> Computing<a></a> time, and I ran<a></a> another<a></a> orientation with<a></a> 10 000 000 photons to be<a></a> sure I am<a></a> not seeing<a></a> statistical<a></a> fluctuations Am I misunderstanding<a></a> the meaning<a></a> of the Rayleigh/ComptVolName<a></a> (actually<a></a>, how is<a></a> this<a></a> leaf<a></a> filled<a></a> when<a></a> a photon has been scattered<a></a> several<a></a> times)? Is it<a></a> another<a></a> feature<a></a> that<a></a> I don’t<a></a> understand<a></a> or am<a></a> I facing<a></a> a bug? <a></a>Cheers, Maximilien -- Maximilien MELISSAS<a></a> Consultant, Alten<a></a> technology<a></a> Image processing<a></a> for CT NDT<a></a> @ Safran composite http://www.alten.com </div> </div> # " Ce courriel et les documents qui lui sont joints peuvent contenir des informations confidentielles, être soumis aux règlementations relatives au contrôle des exportations ou ayant un caractère privé. S'ils ne vous sont pas destinés, nous vous signalons qu'il est strictement interdit de les divulguer, de les reproduire ou d'en utiliser de quelque manière que ce soit le contenu. Toute exportation ou réexportation non autorisée est interdite.Si ce message vous a été transmis par erreur, merci d'en informer l'expéditeur et de supprimer immédiatement de votre système informatique ce courriel ainsi que tous les documents qui y sont attachés." ****** " This e-mail and any attached documents may contain confidential or proprietary information and may be subject to export control laws and regulations. If you are not the intended recipient, you are notified that any dissemination, copying of this e-mail and any attachments thereto or use of their contents by any means whatsoever is strictly prohibited. Unauthorized export or re-export is prohibited. If you have received this e-mail in error, please advise the sender immediately and delete this e-mail and all attached documents from your computer system." #</body> </html>