[Halld-tagger] microscope beam test

[Alexander Somov]

Hello Richard,

Thanks a lot for the information, your plans make
perfect sense, at least for me. I think that at
certain point, we should think of 'reviewing' the
microsope detector (we can discuss it when we come
up with the SOW draft - I am working on it now).


I've checked jumper settings on the fadc board:

channels  0 - 9 were set to 0.5 V range
          10 - 14         to 1 V
          15              to 2 V,
so that the range for the single channels was 0.5 V
and for the sums - 1 V

-

That's what I have in the hardcopy of our logbook:
In the early runs between 117 and 127 we had relatively small
thresholds on both single channel SiPMs and the sums of ~20 mV.
(I recall that we were "playing" with thresholds).

For the production runs, run 129 +
we set the SiPM  thresholds to 60 mV

We can determine exact thresholds from data. But I might not have all
data files here at JLab, as you have ftp'ed most data files to UConn.

Cheers,
       Alex








On Thu, 3 Nov 2011, Richard Jones wrote:

> Alex,
>
> I will keep the idea of another beam test in the Spring in mind.  We have the 
> new preamp design finished, and a run of 3 new pcb's is out on order to the 
> manufacturer now.  A new order of 35 Hamamatsu SiPM's has just gone out as 
> well.  We should have two new completely instrumented preamp boards in the 
> lab by the end of the year.  They have the same form-factor and pin-out as 
> the original, so they can go straight into the prototype detector and work 
> right away.
>
> I will plan to fire up the prototype with the existing electronics on the 
> bench, and measure the pedestal lineshape to extract the single-pixel 
> response.  I have a few things I wonder if you could look up for me.
>
> 1. the discriminator thresholds on all of the SiPM 8 signals (chan. 0-4, 
> 12-14).  If they changed, the date/times when they were changed.
> 2. the gain setting (adc chan/mV) on each channel in the FADC.
>
> Knowing these things will help me cross-check all of my assumptions that I 
> used in extracting the number 350 pixels from the adc spectra.  I agree that 
> the detected pixel count is an important thing to make sure we got right.
>
> Let's plan to review these results at one of our biweekly meetings and assess 
> what risks still exist in our design, which may be reduced by a second run in 
> Hall B in 2012.
>
> -Richard Jones
>
> On 11/3/2011 9:34 AM, Alexander Somov wrote:
>> Hello Richard,
>> 
>> Yes, I agree. I think that once we confirmed the
>> amount of light in the scintillator fiber, the
>> rest of tests can be done on the test bench.
>> 
>> ( though if you get some part of the detector ready
>> by spring, we can test it with the beam again -
>> I volunteer to help with the tests..., but again,
>> it's up to you )
>> 
>> Cheers,
>>          Alex
>> 
>