[Halld-cal] minutes posted

[serguei at jlab.org]

               Dear Elton,
"Elton asked about noise from LED. Serguei said that this is simply low
level noise (~2mV) in the box, which made it difficult to have sensitivity
to single p.e. peak."
There is a misunderstanding. I am sorry for non clean and crumpled
explanation. During the measurement I had the noise (ripple) from LED
driver on my oscilloscope trough "grounding". This ripple is in the same
place in time where is a pulse from the SiPM. And 1 ph.e. pulse has about
the same amplitude like ripple and the oscilloscope picture is not clean.
I closed the LED with a light screen and got the ripple shape (LED driver
worked) and then I subtracted the ripple shape from the SiPM response for
the LED and got very clean few photo electrons pulse shape.
And finally I got pulse charge (in 80 nS gate) distribution with clean
pedestal and photoelectron peaks.

And from page 4 of the presentation you can see that I tested HAMAMATSU
MPPC Type No.: S10362-33-050P 5903, The sample number is 27. Vcp:70.64 V,
Gain (M) is 7.50E+05. The Dark rate is 5.04M at level 0.5 ph.e. and 0.97M
at level 1.5 ph.e..
I got the same 7.50E+05 gain in 80 nS gate, the noise rate was 5 MHz at
0.5 ph.e. level and 1.6 MHz at 1.5 ph.e. level (HAMAMATSU shows 0.97 MHz).
There is enough data for noise excess factor calculation for this SiPM in
the presentation.

Sergey.

>
> Dear collaborators,
>
> I have posted the minutes from today's meeting.
>
> Cheers, Elton.
>
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite # 16
> Newport News, VA 23606
> elton at jlab.org
> (757) 269-7625
> (757) 269-6331 fax
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