[Halld-pid] [EXTERNAL] Re: Start Counter issues

[Beni Zihlmann]

Hi Joerg,

I wrote my own little plugin:
/w/halld-scshelf2101/halld2/home/zihlmann/HallD/work/scmatch

yes there are many reasons why we could lose light. Like light loss due 
to creasing that developed
on the surfaces. That one could probably be tested by investigating the 
reference paddles you still
have at FIU.

cheers,
Beni

On 11/23/22 10:46, Joerg Reinhold wrote:
> Hi Beni,
>
> Gain could be an issue. I could also think of two other possibilities:
>
>   * a loss in transmission through the plastic; I would expect that
>     all other things equal this should be a gradual process, which
>     could be tested.
>   * A loss of transmission from the plastic to the SiPM. I recall that
>     the SiPMs needed to get very accurately adjusted. There is no
>     direct coupling; i.e., there is an air gap of about 160 um; if
>     this somehow increases to 300 um or more, a substantial light loss
>     is expected.The counter has been handled when taken out and put
>     back in before and after CPP. So, something could have happened.
>
>
> What plugin did you run for this?
>
> Also, I probably should join the halld-pid group.
>
> Best,
>
> Joerg
>
>
> Dr. Joerg Reinhold, Professor
> Department of Physics
> Phone: 305-348-6422 | reinhold at fiu.edu​
> ------------------------------------------------------------------------
> *From:* Beni Zihlmann <zihlmann at jlab.org>
> *Sent:* Wednesday, November 23, 2022 10:24
> *To:* halld-pid at jlab.org <halld-pid at jlab.org>; Joerg Reinhold 
> <reinhold at fiu.edu>
> *Subject:* Start Counter issues
>
> Note: This message originated from outside the FIU Faculty/Staff email 
> system.
>
>
> Hi All,
> attached you find a note I cobbled together looking at the start 
> counter data
> and made me worry that we are looking at the issue wrong. This may be not
> a problem with the path correction but rather a "gain" problem.
>
> I plot the TDC_time minus the RF time VS the signal amplitude. And I 
> do this
> for two runs: 73262 (for reference) and a current run 111145.
> These plots are generated at three different positions along the z axis at
> 60cm (middle of the strait section) at 80 cm (bend section) and 92cm
> close to the nose (last two plots).
>
> you can (starting from the last plots) that the issue may be the "gain".
> in run 73262 the minimum ionizing peak is clearly identified and separated
> from the pedestal. This is not so clear for run 111145. Which leads me
> to the conclusion that the earlier plots are indicating we cut into the
> minimum ionizing peak because the gain is too low.
>
> I will go and look at other runs that are closer to the current run period
> with the start counter on. I will also look at what the operating 
> voltages are
> and if they are truly the same as in the past.
>
> Happy Thanksgiving,
> Beni
>
>
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