Matt, The design goal of 32MHz may eventually be achieved, but this is not demonstrated. At the last meeting George agreed that 100MHz is achievable with what he has seen. I would believe something more like 150MHz @ 22C from what I have actually seen, but I am not working with Sensl modules. This depends a lot on temperature, but we agreed that we do not want to have to refrigerate the BCal readout very much. Richard J. Matthew Shepherd wrote: > > Hi All, > > Here's a proposal for setting a BCAL threshold so we can start to > refine the reconstruction a little bit. > > - take dark rate at 32 MHz (design goal from GlueX-doc-795) and assume > this is only single PE rate > - for a 100 ns window this means an average of 3.2 pulses per window > - assume the fADC processing just generates a pedestal subtracted mean > and that dark rate (not electronics noise) dominates the pedestal > - let's assume the DAQ can handle 5% occupancy in the BCAL > - if average is 3.2 dark pulses, the probability of having 7 or more > pulses in a window is 0.04 > > --->> set threshold at 7 photoelectrons > > 7 photoelectrons * ( 26 keV_fiber / pe ) / 12% = 1.5 MeV energy > deposited in cell > > I propose we adjust the threshold to 1.5 MeV (down from 10 MeV) and > work from there. Of course this needs further study, and validation > through whatever bench studies, beam test, etc. etc.. My main goal is > to get around the right order of magnitude so we can make another pass > at the reconstruction algorithm which will behave very differently > with this much lower threshold. Does anyone see a serious flaw with > this? > > -Matt >
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