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Fernando,<br>
<br>
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.<br>
<br>
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.<br>
<br>
No?<br>
<br>
-- Mark<br>
<br>
<div class="moz-cite-prefix">On 04/18/2014 11:48 AM, Fernando J
Barbosa wrote:<br>
</div>
<blockquote cite="mid:53514948.3080301@jlab.org" type="cite">Hi
Mark,
<br>
<br>
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.
<br>
<br>
Best regards,
<br>
Fernando
<br>
<br>
<br>
On 4/18/2014 11:42 AM, Mark Ito wrote:
<br>
<blockquote type="cite">Folks,
<br>
<br>
Please find the minutes below and at
<br>
<br>
<a class="moz-txt-link-freetext" href="https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_17,_2014#Minutes">https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_17,_2014#Minutes</a>
<br>
<br>
-- Mark
<br>
___________________________________________________________________
<br>
<br>
GlueX Start Counter Meeting, April 17, 2014
<br>
Minutes
<br>
<br>
Present:
<br>
* FIU: Werner Boeglin, Eric Pooser
<br>
* JLab: Fernando Barbosa, Eugene Chudakov, Mark Ito
(chair)
<br>
<br>
Electronics
<br>
<br>
Fernando gave us a report.
<br>
<br>
All fabrication of ST-1, ST-2, and ST-3 boards is done. The
signal
<br>
split for ADC and TDC is now done on ST-3, not on ST-2 as
before. The
<br>
ST-3 testing is complete. The pre-testing (checking SiPM
connections,
<br>
etc.) of the ST-1s is done and the 10 ST-2s are being
tested now. That
<br>
should be done by tomorrow. After that the 30 channels on
the ST-1s
<br>
will be tested with a laser in the dark box. Also a test
will be done
<br>
to measure the electronic component of time resolution
using the laser.
<br>
It has a 100 ps rise-time and negligible jitter. This will
be done with
<br>
a complete chain from ST-1 to ST-2 to ST-3 to discriminator
to TDC. A
<br>
diffuser is used so that all four SiPMs can be illuminated.
A set of a
<br>
few amplitudes will be measured, and both ADC-bound and
TDC-bound
<br>
signals will be looked at. All tests should be done by the
end of the
<br>
month.
<br>
<br>
On the mechanical side, there is a plan to do a test fit of
the
<br>
electronics on the aluminum support ring once that becomes
available.
<br>
<br>
When the items have been shipped to FIU, Nick Sandoval will
go down and
<br>
help to get the test set-up started. Fernando needs about
one month
<br>
notice to arrange travel.
<br>
<br>
We had a discussion on the scheme for making sure that the
ST-1 boards
<br>
do not short against the aluminum support ring. [Added in
press: this
<br>
discussion assumed that there is no allowance for spacing
washers in
<br>
the design. This turned out not to be the case; a 40 mil
washer is
<br>
called out in the drawings. This rendered the discussion
moot.]
<br>
<br>
The group reminded Mark that we will not ship ADCs, TDCs,
or
<br>
discriminators to FIU for testing the detector there. FIU
will use
<br>
their existing read-out electronics. We will send an MPOD
and all
<br>
cables that connect the ST-2s to the ST-3. We discussed how
many signal
<br>
cables need to be shipped (those running from the ST-3). We
decided to
<br>
defer a decision on that.
<br>
<br>
We decided that we should do a test mechanical assembly at
JLab before
<br>
shipping the support structure to FIU, including as much as
is
<br>
practical: support ring to target support, ST-3 on
installation cart,
<br>
cables from ST-2 to ST-3, etc. The exact plan needs to be
worked out.
<br>
<br>
Schedule
<br>
<br>
Werner laid out a very rough schedule given what we know
now.
<br>
1. scintillators arrive at FIU: mid-May
<br>
2. scintillator testing and detector assembly done: end of
June
<br>
3. Nick visit: early July
<br>
4. testing done: end of July
<br>
5. ship to JLab: mid-August
<br>
<br>
Assembly Jig
<br>
<br>
Eric presented the final design for the assembly jig. See
his slides
<br>
([18]PDF, [19]Powerpoint) for details. Eric plans to call
Chuck Hutton
<br>
and discuss the design as well.
<br>
<br>
Progress at McNeal
<br>
<br>
[Added in press: Eric talked to Robert McNeal just after
the meeting
<br>
and sent in this report.]
<br>
<br>
All 50 paddles have been inspected and have passed the
initial QA
<br>
check. Machining of the paddles has not yet commenced. They
are waiting
<br>
for the machines to finish other jobs. However, production
should begin
<br>
within a week.
<br>
<br>
Robert quoted that the paddles will be shipped out to FIU,
no later
<br>
than 05/02/2014 which is right at the 4 week lead time we
were quoted.
<br>
<br>
Eric provided Robert with the most up to date mechanical
drawing of the
<br>
paddles. There were no substantial differences between the
two drawings
<br>
and this update will have no negative consequences.
<br>
<br>
Robert mentioned that they do quantify the final dimensions
of the
<br>
paddles after they are machined. This is done both
optically and by
<br>
machine. Standard operating procedure dictates that they
will only
<br>
measure approximately 8 of the 50 paddles. He is willing to
provide us
<br>
with this data. It is possible for them to inspect all 50
paddles and
<br>
provide us with their associated measurements for a minor
inspection
<br>
fee initially estimated at $200.00. Further discussions
will be made
<br>
regarding whether we should purchase this inspection data.
<br>
<br>
References
<br>
<br>
18.
<a class="moz-txt-link-freetext" href="https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pdf">https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pdf</a>
<br>
19.
<a class="moz-txt-link-freetext" href="https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pptx">https://halldweb1.jlab.org/talks/2014-2Q/Finalized_Assembly_Jig.pptx</a>
<br>
<br>
</blockquote>
<br>
<br>
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<br>
<pre wrap="">_______________________________________________
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Mark M. Ito, Jefferson Lab, <a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295
</pre>
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