[Halld-pid] Minutes, GlueX TOF Meeting, October 27, 2011

[Mark M. Ito]

Folks,

Find the minutes at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_27,_2011 
and below as text.

-- Mark
_____

GlueX TOF Meeting, October 27, 2011

Minutes

Present:
* FSU: Sasha Ostrovidov
* JLab: Eugene Chudakov, Chuck Hutton, Mark Ito (chair), Simon
Taylor, Tim Whitlatch, Beni Zihlmann

Review of Minutes from the Last Meeting

We went over the [29]minutes of the October 13th meeting.

Efficiency with Reduced Gain

Beni summarized his estimates of how low we could go with PMT gain and
still preserve good efficiency for minimum ionizing particles. He
assumes we want to operate at 20 μA current per tube and are running at
10^7 photons per second. The would give a tube life of roughly two
years. Then on all but the innermost split counters, and a 20 mV
discriminator threshold we can maintain good efficiency all along the
counter without amplifiers. See his [31]wiki page for details.

Other Items

* Chuck has been in contact with Ian Winger. Ian will send a new
model of the half-width light guide.
* Mark sent a response about our rates and current to the Hamamatsu
engineer who requested information.
* We still need new milestones for the SOW from Paul.
* Mark circulated [33]Fernando Barbosa's schematics for the
splitters. Sasha checked his splitters against the values listed
and found agreement. The origin of the [34]reflections reported
last time remains a mystery.
* Sasha checked least count of his CAEN ADC and got a value of 0.25
pC, as advertised, within about 5%.
* FSU has not had a look at the 8-stage tubes yet.

Mechanical Design

Chuck reported progress on the support scheme for the modules. See
[36]his drawings (added in press) for the latest scheme.

Tim stated that they are pushing forward on the design for holding the
steel next.

We discussed how to deal with the possibility of having to replace
tubes.
* Beni will ask Dave Mack about what is done in Hall C and will ask
Bogdan W??? about Hall A.
* We discussed the possibility of removing the entire TOF array for a
round of tube replacement.
+ In this case Eugene wondered if the detector can be supported
to give horizonal surfaces for the glue joints that are being
redone.
* Choice of glue must be made with replacement in mind.
* Beni proposed that we use grease to facilitate replacement.
* We will clearly have to have a mechanical design that allows
replacement of tubes.

Prototype Progress

Sasha is now doing measurements with the same splitters on all six
signals. It takes about two weeks for one configuration. He is working
with the 50/50 split now. He will change to 80/20 next.

Contract

We are badly behind the schedule we proposed in the APP and need to get
a package to procurement ASAP. Tim pointed out that we have often
started the procurement process without the final version of specs for
other contracts.

Retrieved from 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_27,_2011

References

29. 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_13,_2011#Minutes
31. 
https://halldweb1.jlab.org/wiki/index.php/Detector_Rates_and_Lifetime#Operating_PMT_at_0.02mA
33. https://halldweb1.jlab.org/wiki/images/b/b7/Splitter_%26_Inverter.pdf
34. https://halldweb1.jlab.org/talks/2011-4Q/Termination%20at%20PMT.html
36. https://halldweb1.jlab.org/talks/2011-4Q/tof_10_27_11.pptx