<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <style type="text/css" style="display:none;"></style> </head> <body dir="ltr"> <div id="divtagdefaultwrapper" dir="ltr" style="font-size: 12pt; color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols;"> <p><br> </p> <br> <br> <div style="color:rgb(0,0,0)"> <div> <hr tabindex="-1" style="display:inline-block; width:98%"> <div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Paul Betteridge <paul.betteridge@adaptiximaging.com><br> <b>Sent:</b> Saturday, 10 June 2017 3:40 a.m.<br> <b>To:</b> Emmanuel Marfo<br> <b>Subject:</b> Re: [Gate-users] Help on simulating x-ray tube</font> <div> </div> </div> </div> <font size="2"><span style="font-size:10pt"> <div class="PlainText">Dear Emmanuel,<br> <br> > Please, it appears the problem is coming from my tungsten(anode). I <br> > change the anode to copper and I had photons coming out of it. I think <br> > my problem has been the tungsten. Please is there any possible solution <br> > to these or Is there a way I can get photons from the tungsten.<br> <br> Yes, I think your problem is, to some degree, because of the tungsten; <br> because tungsten is such a good absorber of x rays.<br> <br> I ran your script with 1e5 primaries, and it produced a small number of <br> photons - as in the attached image.<br> <br> I think the problem is this: Gate uses "cuts" as a way to speed up <br> simulations (by removing low energy particles that are not actually <br> going to be 'useful'.) See: <br> <a href="http://wiki.opengatecollaboration.org/index.php/Users_Guide_V8.0:Cut_and_Variance_Reduction_Technics" id="LPlnk258581" previewremoved="true">http://wiki.opengatecollaboration.org/index.php/Users_Guide_V8.0:Cut_and_Variance_Reduction_Technics</a> <div id="LPBorder_GT_14970459198230.824171298046483" style="margin-bottom:20px; overflow:auto; width:100%; text-indent:0px"> <table id="LPContainer_14970459198140.844791515159389" cellspacing="0" style="width:90%; background-color:rgb(255,255,255); overflow:auto; padding-top:20px; padding-bottom:20px; margin-top:20px; border-top:1px dotted rgb(200,200,200); border-bottom:1px dotted rgb(200,200,200)"> <tbody> <tr valign="top" style="border-spacing:0px"> <td id="TextCell_14970459198180.3719367699305234" colspan="2" style="vertical-align: top; padding: 0px; display: table-cell; position: relative;"> <div id="LPRemovePreviewContainer_14970459198180.7580914820464693"></div> <div id="LPTitle_14970459198180.4116930910991361" style="top:0px; color:rgb(22,54,106); font-weight:normal; font-size:21px; font-family:wf_segoe-ui_light,"Segoe UI Light","Segoe WP Light","Segoe UI","Segoe WP",Tahoma,Arial,sans-serif; line-height:21px"> <a id="LPUrlAnchor_14970459198200.046748500848339036" href="http://wiki.opengatecollaboration.org/index.php/Users_Guide_V8.0:Cut_and_Variance_Reduction_Technics" target="_blank" style="text-decoration:none">Users Guide V8.0:Cut and Variance Reduction Technics ...</a></div> <div id="LPMetadata_14970459198200.07625789046828046" style="margin:10px 0px 16px; color:rgb(102,102,102); font-weight:normal; font-family:wf_segoe-ui_normal,"Segoe UI","Segoe WP",Tahoma,Arial,sans-serif; font-size:14px; line-height:14px"> wiki.opengatecollaboration.org</div> <div id="LPDescription_14970459198210.9050910314786553" style="display:block; color:rgb(102,102,102); font-weight:normal; font-family:wf_segoe-ui_normal,"Segoe UI","Segoe WP",Tahoma,Arial,sans-serif; font-size:14px; line-height:20px; max-height:100px; overflow:hidden"> Production threshold, step limiter and special cuts Production threshold. To avoid infrared divergence, charged particles processes (ionization and bremsstrahlung ...</div> </td> </tr> </tbody> </table> </div> <br> <br> <br> Partly because of the way they are specified, and partly because of the <br> rather effective absorption of photons by tungsten, your simulation was <br> set up to only produce photons with an energy greater than about 106 <br> keV. There are not many of these.<br> <br> You can check the cuts applied by adding<br> <br> /gate/physics/displayCuts<br> <br> I recommend this for every simulation, just so you can check what is <br> happening.<br> <br> If you add a line like this:<br> <br> /gate/physics/Gamma/SetCutInRegion anode 10 um<br> <br> after the physics setup, you should find that the energy limit is much <br> reduced. I've attached my modified script for you to compare.<br> <br> Specifying the cut energy using a length isn't that convenient for the <br> type of simulation you are trying to do. It can make a significant <br> difference to the time a simulation takes to run though, so it is <br> worthwhile trying to establish a sensible value.<br> <br> I am still a bit concerned about you electron source, which seems to <br> spread electrons over a wide volume. I don't suppose the real device is <br> like that.<br> <br> Don't forget that it is better to keep all messages on the mailing list, <br> because (a) other people may be able to help (b) other people may find <br> the correspondence useful.<br> <br> Best wishes<br> <br> Paul<br> <br> -- <br> Paul Betteridge<br> Adaptix Imaging<br> </div> </span></font></div> </div> </body> </html>