[Halld-pid] ADC

[Alexander Ostrovidov]

On Friday, September 30, 2011, Beni Zihlmann wrote:
> Hi Sasha,
> in the link
> https://halldweb1.jlab.org/talks/2011-3Q/ADC%20spectra%20and%20Time-walk%20corrections_files/
> you show an ADC spectrum of a paddle PMT: adc_l_par_nottrig.gif.
> what is the HV of the PMT set at and what type of ADC are you using?
> 
> cheers,
> Beni
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> 
Beni,

This particular plot is done with:

1) CAEN ADC v265 in 12-bit mode. This  corresponds to 
0.25 pC per count

2) 10-stage PMT with a nominal gain of 1.5*10^6 (at 1750 V). 
However, it was used at 2000 V in this particular measurement. 
So, its actual gain is unknown in this case.

3) What makes things more complications is a signal attenuation
on its way from PMT anode to the ADC due to a 50-50 splitter, 
a 50 Ohm terminator right at the PMT,  and 150ft of cable. Right now, 
I'm trying to measure what is the correction coefficient I need to apply 
to compensate for this attenuation. I should have an estimate of the 
number of photoelectrons later today.

Sasha