[Gate-users] Impossible (or Improbable ) timestamps for Randoms Coincidences

[Paul Vaska]

We have seen this as well and it seems like a bug.  It looks like the  
coincidence processor is using a different time than the time  
reported in the output data.  For example, if the coincidence code  
uses the exact event time and the output code reports the event time  
after time resolution blurring, then you can have events like this.   
But we've not proven that this is the specific cause.

Paul

Paul Vaska, Ph.D.
Medical Department, Building 490
Brookhaven National Laboratory
Upton, NY 11973
vaska at bnl.gov (631)344-6228 fax:(631)344-4146



On Jun 30, 2008, at 1:45 PM, KB wrote:

> Hello all.
>
>     Plotting (time1-time2) for all the randoms coincidences, I  
> notice that the lower value is a sharp cutoff (just as I expect)  
> but the higher value is over and beyond the coincidence window.  
> With my coincidence window set to 6 ns, I see (time1-time2) values  
> as high as 89 ns.
>
> I have plotted (time1-time2) and uploaded the plot here: http:// 
> img337.imageshack.us/img337/4598/gatetalkhm9.gif
>
> The relevant lines from my digitiser are:
>
> /gate/digitizer/Coincidences/setWindow 6.0 ns
> /gate/digitizer/Coincidences/minSectorDifference 7
> /gate/digitizer/Coincidences/MultiplesPolicy takeAllGoods
> /gate/digitizer/name delay
> /gate/digitizer/insert coincidenceSorter
> /gate/digitizer/delay/setWindow 6.0 ns
> /gate/digitizer/delay/setOffset 500.0 ns
> /gate/digitizer/delay/MultiplesPolicy  takeAllGoods
>
>
> I am interested in knowing why I get randoms coincidences beyond  
> the coincidence window. Thanks for any help.
>
> Karthik.
> <GATE_Talk.jpg>
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