<div dir="ltr">Hello Maximilien, <div> </div><div>we are currently working on an approach that could decrease the computation time (hopefully by a least 1 order of magnitude). However, this approach which is based on the forced detection technique, is still in development and not yet available. In the meantime, try to be sure to avoid any electron generation. </div> <div> </div><div>David</div> </div><div class="gmail_extra"> <div class="gmail_quote">On Fri, Feb 7, 2014 at 3:03 PM, MELISSAS Maximilien (SAFRAN) <<a href="mailto:maximilien.melissas-alten@safran.fr" target="_blank">maximilien.melissas-alten@safran.fr</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div> <div style="direction:ltr;font-size:x-small;font-family:Tahoma"> <a></a>Dear Gate-users<a></a> I am<a></a> using<a></a> Gate<a></a> to simulate<a></a> a CT acquisition chain<a></a> (GE tomex<a></a> L 450) used<a></a> for CT analysis<a></a> of aeronautical<a></a> parts. The main issue I am<a></a> facing<a></a> is<a></a> computing<a></a> time, especially<a></a> if I want<a></a> to simulate<a></a> a full scan (2400 projections at<a></a> I= 2ma<a></a>, V = 350 kV. (One of) my<a></a> “test” setup is<a></a> an epoxy<a></a> cylinder<a></a> located<a></a> 50 cm from<a></a> the tube, with<a></a> the detector at<a></a> 1m<a></a> from<a></a> the tube, if I propagate<a></a> 500 000 (as a benchmark) photons the “user”computing<a></a> times are the following<a></a>: 31.15 seconds without<a></a> optimization<a></a> (Only<a></a> setting the simulation as /fast<a></a>/ to avoid<a></a> losing<a></a> one hour<a></a> computing<a></a> a 2048x2048<a></a> pixels grid<a></a>) 30.8 seconds if I play<a></a> with<a></a> MaxStepSize<a></a> (Actually<a></a>, if I do /gate<a></a>/physics<a></a>/SetMaxStepSizeInRegion<a></a> world 15.0 mm, is<a></a> the step<a></a> size reset to a normal value when<a></a> entering<a></a> another<a></a> material<a></a> ? ) 31.71 seconds if I set VRT<a></a> to 10 (as in the benchmarkCT<a></a>/vrt<a></a> example<a></a>) This important CPU<a></a> time makes<a></a> me fear<a></a> that<a></a> I cannot<a></a> compute<a></a> nor<a></a> a realistic<a></a> amount<a></a> of photon, neither<a></a> a realistic<a></a> number<a></a> of projections, so<a></a> I need<a></a> to find<a></a> some<a></a> way<a></a> to reduce<a></a> computing<a></a> time while<a></a> keeping<a></a> useful<a></a> informations) Is-there<a></a> any<a></a> option similar<a></a> to thinning<a></a>/weighting<a></a> (but for primaries<a></a> since<a></a> I am<a></a> not interested<a></a> in secondary<a></a> electrons<a></a>) to increase<a></a> luminosity<a></a> without<a></a> increasing<a></a> computing<a></a>-time? Is there<a></a> any<a></a> other<a></a> way<a></a> to reduce<a></a> the simulation time? Does<a></a> the vrt<a></a> increase<a></a> the weight<a></a> of a photon hitting<a></a> the detector and thus<a></a> increase<a></a> virtually<a></a> the number<a></a> of photons? (I haven't<a></a> tried<a></a> yet<a></a> to generate<a></a> images with<a></a> the vrt<a></a> enabled<a></a>) <a></a>Another question, even<a></a> though<a></a> the default source is<a></a> conical<a></a>, I'd<a></a> like<a></a> to take<a></a> into<a></a> account<a></a> the Gaussian-shape<a></a> of the X-ray spot, is<a></a> there<a></a> advanced<a></a> setting of the source in the macros? If not-is<a></a> there<a></a> any<a></a> Cpp<a></a> example<a></a>? A last question, how do I find<a></a> the history<a></a> of a hit, when<a></a> parsing<a></a> the ntuple<a></a>, can<a></a> I find<a></a> information about the hit's<a></a> history<a></a>, whether<a></a> the photon has been scattered<a></a>, and through<a></a> which<a></a> material<a></a> has it<a></a> been propagated<a></a> ? i.e. how do I make<a></a> the difference<a></a> between<a></a> 0 0.0116 0.013 -150 0.156 0 0 0 world_phys<a></a> initStep<a></a> 1 0.433 -4.18 -12 0.156 0 138 138 epoxyCylinder_phys<a></a> Transportation 2 0.458 -4.42 -3.97 0.156 0 8.02 146 CCylinder_phys<a></a> Transportation 3 0.482 -4.66 3.97 0.156 0 7.95 154 epoxyCylinder_phys<a></a> Transportation 4 0.506 -4.9 11.8 0.156 0.000291 7.81 162 epoxyCylinder_phys<a></a> Compton 5 0.539 -4.87 12 0.156 0 0.216 162 world_phys<a></a> Transportation 6 22 12.5 150 0.156 0 141 303 pixel_phys<a></a> Transportation And 0 -0.0249 -0.017 -150 0.114 0 0 0 world_phys<a></a> initStep<a></a> 1 -4.21 0.707 -11.2 0.114 0 139 139 epoxyCylinder_phys<a></a> Transportation 2 -4.88 0.823 11 0.114 0 22.2 161 world_phys<a></a> Transportation 3 -9.06 1.55 150 0.114 0 139 300 pixel_phys<a></a> Transportation I guess<a></a> I should<a></a> set some<a></a> actors<a></a>, but I do not find<a></a> any<a></a> clear<a></a> examples<a></a> in the documentation. <a></a>Thanks for your<a></a> answers<a></a>/help, Cheers<a></a>, Maximilien </div> # " Ce courriel et les documents qui lui sont joints peuvent contenir des informations confidentielles, �tre soumis aux r�glementations relatives au contr�le des exportations ou ayant un caract�re priv�. 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