<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Hi ashley, Ashley Devarim a écrit : <blockquote cite="mid:BAY124-W176FAD29F7CCB7FA2E362FA2B0@phx.gbl" type="cite"> <pre wrap="">Hi David, Thank you very much for your answer, would you mind please if you take a look at my questions below : </pre> <blockquote type="cite"> <pre wrap="">Hello, actually, I don't understand what you want to set up... The setLambda parameter (7.57 mus in your exemple) is equal to the mean time between to consecutives noise events in a Poisson distributed noise source. The inverse of this value is the noise frequency, thus. </pre> </blockquote> <pre wrap=""> 1) but the difference time distribution is an exponential and the setLambda parameter is the power of the distribution, even in this case the setLambda parameter would be simply the inverse of the noise frequency ? </pre> </blockquote> Actually, you can deal with any kind of time interval distribution. The one given in the example correspond to an exponential distribution, because a Poisson's process imply such model of time interval distribution. So if your noise source follow the Poisson law, you can keep this distribution (and adapt the setLambda parameter to your noise frequency). If not, a generic way to define your own distribution is to use <pre wrap="">/gate/distributions/insert File</pre> and specify a file that you prepared and which will contain your distribution (table 8.1, page 97 in the v3.1.2 GATE user guide is regrouping parameters for file based distribution). <blockquote cite="mid:BAY124-W176FAD29F7CCB7FA2E362FA2B0@phx.gbl" type="cite"> <pre wrap="">2) For example if I have a noise values varying between 0 and 90 keV and mean value = 60 keV , what would be the setMean and setSigma parameters in this case ? </pre> </blockquote> Here again, the example correspond to a Gaussian distributed noise (Gaussian in terms of energy spectrum, and Poissonian in terms of time distribution, so). If this doesn't corresponds to the noise you want to modelize, you can always use the general purpose File distribution to fit your needs. In the example you gave, you are specifying the min/max value of the distribution, as well as its mean value. This is not sufficient to characterize the energy spectrum. If this spectrum can be modelized by a Gaussian, an exponential or a flat distribution, you can use one of the specific forms of distributions given in the table 8.2 already mentioned. In any other case, you should use the generic File distribution method. <blockquote cite="mid:BAY124-W176FAD29F7CCB7FA2E362FA2B0@phx.gbl" type="cite"> <pre wrap=""></pre> <blockquote type="cite"> <pre wrap="">Concerning, the eventID number, it is due to the fact that noise events are not produced by physical interaction of particles with detectors (which can be attached to a particle emission event number, which is eventID). The noise events are described as independent source of detector signal, not correlated to any physical particle emission, and are then marked with the special event number (-2). </pre> </blockquote> <pre wrap=""> 3) here the reason for my question was, that the noise events participate to the coincidences events like a particle emission events and I was wondering if this is happening in real life ? I thought that noise should be mixed with the signal and not seen as separated event ( like energy blurring )? what do you think please ? </pre> </blockquote> Actually, it depends on what you mean by "coincidence" If you're using the coincidence feature of gate (/gate/digitizer/coincidence/...) the module doesn't care about the eventID and so, the noise events will be merged with "physical" events for coincidences (this, because the time flag of the noise events are distributed along the total time of your simulation). But if you're using a test on eventID to determine if two events are in coincidence (e.g. eventID of data1 == eventID of data2), so, this test can't deal with noise events, because eventID is actually a marker of the particle source creation marker. <blockquote cite="mid:BAY124-W176FAD29F7CCB7FA2E362FA2B0@phx.gbl" type="cite"> <pre wrap=""> Kind Regards Ashley </pre> </blockquote> Best regards, D. Guez </body> </html>