[Halld-pid] Start Counter Meeting Minutes, April 17, 2014

[Mark Ito]

Fernando,

At one point there was concern about opening a 1.25 mm gap by installing 
50 mil spacers. If such a spacer was already in the drawings, then no 
such gap would open. So I assumed that we were discussing on the basis 
of a no-spacer drawing. After the meeting we found that that was the 
wrong basis; spacers are in the drawing.

It is true that coming into the meeting we were all thinking that the 
spacer was the default plan, but mid-meeting we started worrying that 
they were not in the drawing. In that case something would have had to 
change and the pocket idea started to look good. Uniformity of the 
spacing using spacers may indeed be an issue, but I don't think it was 
the one driving the discussion.

No?

   -- Mark

On 04/18/2014 11:48 AM, Fernando J Barbosa wrote:
> Hi Mark,
>
> Maybe I missed something but the spacers were always part of the 
> design. The question, as I understood at the meeting, was whether the 
> spacers provided enough precision and uniformity during attachment of 
> the ST1s.
>
> Best regards,
> Fernando
>
>
> On 4/18/2014 11:42 AM, Mark Ito wrote:
>> Folks,
>>
>> Please find the minutes below and at
>>
>> https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_17,_2014#Minutes 
>>
>>
>>     -- Mark
>> ___________________________________________________________________
>>
>> GlueX Start Counter Meeting, April 17, 2014
>> Minutes
>>
>>      Present:
>>        * FIU: Werner Boeglin, Eric Pooser
>>        * JLab: Fernando Barbosa, Eugene Chudakov, Mark Ito (chair)
>>
>> Electronics
>>
>>      Fernando gave us a report.
>>
>>      All fabrication of ST-1, ST-2, and ST-3 boards is done. The signal
>>      split for ADC and TDC is now done on ST-3, not on ST-2 as 
>> before. The
>>      ST-3 testing is complete. The pre-testing (checking SiPM 
>> connections,
>>      etc.) of the ST-1s is done and the 10 ST-2s are being tested 
>> now. That
>>      should be done by tomorrow. After that the 30 channels on the ST-1s
>>      will be tested with a laser in the dark box. Also a test will be 
>> done
>>      to measure the electronic component of time resolution using the 
>> laser.
>>      It has a 100 ps rise-time and negligible jitter. This will be 
>> done with
>>      a complete chain from ST-1 to ST-2 to ST-3 to discriminator to 
>> TDC. A
>>      diffuser is used so that all four SiPMs can be illuminated. A 
>> set of a
>>      few amplitudes will be measured, and both ADC-bound and TDC-bound
>>      signals will be looked at. All tests should be done by the end 
>> of the
>>      month.
>>
>>      On the mechanical side, there is a plan to do a test fit of the
>>      electronics on the aluminum support ring once that becomes 
>> available.
>>
>>      When the items have been shipped to FIU, Nick Sandoval will go 
>> down and
>>      help to get the test set-up started. Fernando needs about one month
>>      notice to arrange travel.
>>
>>      We had a discussion on the scheme for making sure that the ST-1 
>> boards
>>      do not short against the aluminum support ring. [Added in press: 
>> this
>>      discussion assumed that there is no allowance for spacing 
>> washers in
>>      the design. This turned out not to be the case; a 40 mil washer is
>>      called out in the drawings. This rendered the discussion moot.]
>>
>>      The group reminded Mark that we will not ship ADCs, TDCs, or
>>      discriminators to FIU for testing the detector there. FIU will use
>>      their existing read-out electronics. We will send an MPOD and all
>>      cables that connect the ST-2s to the ST-3. We discussed how many 
>> signal
>>      cables need to be shipped (those running from the ST-3). We 
>> decided to
>>      defer a decision on that.
>>
>>      We decided that we should do a test mechanical assembly at JLab 
>> before
>>      shipping the support structure to FIU, including as much as is
>>      practical: support ring to target support, ST-3 on installation 
>> cart,
>>      cables from ST-2 to ST-3, etc. The exact plan needs to be worked 
>> out.
>>
>> Schedule
>>
>>      Werner laid out a very rough schedule given what we know now.
>>       1. scintillators arrive at FIU: mid-May
>>       2. scintillator testing and detector assembly done: end of June
>>       3. Nick visit: early July
>>       4. testing done: end of July
>>       5. ship to JLab: mid-August
>>
>> Assembly Jig
>>
>>      Eric presented the final design for the assembly jig. See his 
>> slides
>>      ([18]PDF, [19]Powerpoint) for details. Eric plans to call Chuck 
>> Hutton
>>      and discuss the design as well.
>>
>> Progress at McNeal
>>
>>      [Added in press: Eric talked to Robert McNeal just after the 
>> meeting
>>      and sent in this report.]
>>
>>      All 50 paddles have been inspected and have passed the initial QA
>>      check. Machining of the paddles has not yet commenced. They are 
>> waiting
>>      for the machines to finish other jobs. However, production 
>> should begin
>>      within a week.
>>
>>      Robert quoted that the paddles will be shipped out to FIU, no later
>>      than 05/02/2014 which is right at the 4 week lead time we were 
>> quoted.
>>
>>      Eric provided Robert with the most up to date mechanical drawing 
>> of the
>>      paddles. There were no substantial differences between the two 
>> drawings
>>      and this update will have no negative consequences.
>>
>>      Robert mentioned that they do quantify the final dimensions of the
>>      paddles after they are machined. This is done both optically and by
>>      machine. Standard operating procedure dictates that they will only
>>      measure approximately 8 of the 50 paddles. He is willing to 
>> provide us
>>      with this data. It is possible for them to inspect all 50 
>> paddles and
>>      provide us with their associated measurements for a minor 
>> inspection
>>      fee initially estimated at $200.00. Further discussions will be 
>> made
>>      regarding whether we should purchase this inspection data.
>>
>> References
>>
>>     18. 
>> https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pdf
>>     19. 
>> https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pptx
>>
>
>
>
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-- 
Mark M. Ito, Jefferson Lab, marki at jlab.org, (757)269-5295

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