[Halld-cal] BCAL - Scaler Hot Channels

[Elton Smith]

Hi Tegan and Zisis,

It appears that the "hot" channels are only seen in the TDCs, which 
means that it is likely the discriminator or the TDC signal that feeds 
the discriminator. We will continue to monitor the channels and 
determine their location. I would also like to see the rates with beam. 
My recollection from last fall is that the behavior of various "hot" 
channels changed with beam conditions. Mark thinks that the individual 
discriminator channels have different thresholds even when they are set 
to the same value, so a variation in the threshold could account for 
some of this behavior. Switching cables with neighbors could indicate 
the source of the high rates. Unless the rate with beam affects the 
amount of data we are taking, we may wish to simply live with this.

Cheers, Elton.

Elton Smith
Jefferson Lab MS 12H3
12000 Jefferson Ave STE 4
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax

On 3/23/15 4:10 PM, Zisis Papandreou wrote:
> Hi BCAL team:
>
> Tegan has run several investigations connected to the issue of the 
> handful of "hot scalers" on the BCAL.  He does not see evidence for 
> this in the ADCs of TDCs, using the plugins described below.
>
> As Mark suggested during our last meeting, a cable swap can would tell 
> us whether it is the scalers that have the problem or it is in the 
> disciminator->TDC route.
>
> Any other ideas?  Can it be something in the plugins that masks seeing 
> the effect? We think not, but perhaps we overlooked something.
>
> Cheers and thanks, Zisis...
>
> Begin forwarded message:
>
>> *From: *beattite <beattite at uregina.ca <mailto:beattite at uregina.ca>>
>> *Subject: **Hot Channels*
>> *Date: *March 23, 2015 at 1:49:15 PM CST
>> *To: *Zisis Papandreou <zisis at uregina.ca <mailto:zisis at uregina.ca>>
>>
>> Using a version of the DAQTreeBCAL plugin, we don't see increased 
>> number of events in the 'hot' channels from the ADC (BCALdigi tree) 
>> or from the TDC (BCALTDCdigi tree).  The 'w_integral' (integral of 
>> the waveform) distributions for the 'hot' channels compared to normal 
>> channels seem to be indistinguishable.  The waveforms, as well, look 
>> the same.
>>
>> As Elton suggested, we might not see the effects of the hot channels 
>> in the ADCs if there's something going on in the TDC line.  But, it 
>> is odd that the scalars see huge rates for these channels while the 
>> TDC is not recording an increased number of events if the input for 
>> both is coming from the same discriminator.
>>
>> If we could do some cable-swapping tests like Mark mentioned at the 
>> last meeting, that might be best for trying to figure out what's 
>> happening.
>
>
> Dr. Zisis Papandreou
> Professor of Physics, Ph.D., P.Phys.
> ---------------------------------------------------------
> Department of Physics
> University of Regina
> 3737 Wascana Parkway
> Regina, SK  S4S 0A2 CANADA
>
> *Phone: (306) 585-5379*
> Fax: (306) 585-5659
> Email: zisis at uregina.ca <mailto:zisis at uregina.ca>
> Website: 
> http://www.uregina.ca/science/physics/faculty-staff/faculty/zisis-papandreou.html 
> <http://kronos.phys.uregina.ca/%7Ezisis/professional/>
>
>
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