[Hps-ecal] pedestals and pileup

[Stepan Stepanyan]

Nathan,

Your last point is probably the best way to go.
Can we run high rate pulsar (10kHz) trigger at the beginning
and the end of run each run for pedestals?.

Stepan

On 1/11/15 9:22 AM, Nathan Baltzell wrote:
> Hi Andrea,
>
> I think you are right:  we should use the pedestal from mode-7 data.  And there is a 3rd
> option I mentioned on page 3 that I think may be better than event-by-event or run-averaged:
> keep a running average of the pedestal over the last N seconds/events.
>
> -Nathan
>
>
> On Jan 11, 2015, at 6:48 AM, Andrea Celentano <andrea.celentano at ge.infn.it> wrote:
>
>> Hi Nathan,
>> this is a very interesting study. I'd like to add a comment to the discussion (something we already mentioned some time ago at one of the Ecal meetings)
>>
>> - In FADC mode 7, for every event and for every channell over threshold, we record 4 numbers:
>> * Energy (in FADC counts, i.e the sum of the samples around the signal peak)
>> * Time
>> * Pedestal (average of the first 4 samples, in FADC counts)
>> * Signal amplitude (in FADC counts, i.e. the max signal height)
>>
>> We can think about 2 ways of subtracting the pedestal using these data
>>
>> 1) Event by event, as energy - pedestal * fadc_integration_window_width
>> 2) On average, computing the average pedestal for a given channel over the run, and then subtracting it as before
>>
>> If we expect the pedestal to be roughly constant during a run (if the beam current is constant), then I expect the second solution to be better than the first one.
>> With the first solution, event by event the pedestal noise affects the energy resolution.
>>
>>
>> Andrea
>>
>> On 01/10/2015 10:48 PM, Nathan Baltzell wrote:
>>> Hi Everyone,
>>>
>>> Here is a recent look at some pedestal studies.  It appears they have an effect from pileup.
>>> It’s not significant for many channels, but for high rate channels near the beam I think we
>>> are going to want to correct it.  It would be interesting to see if Luca’s gain calibration sees
>>> any current-dependence coming from incorrect pedestals.
>>>
>>> -Nathan
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Hps-ecal mailing list
>>>
>>> Hps-ecal at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/hps-ecal
>
> _______________________________________________
> Hps-ecal mailing list
> Hps-ecal at jlab.org
> https://mailman.jlab.org/mailman/listinfo/hps-ecal