[Halld-pid] Minutes, GlueX Start Counter Meeting, April 19, 2012

[Mark M. Ito]

Find the minutes below and at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_19,_2012#Minutes 
.
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GlueX Start Counter Meeting, April 19, 2012
Minutes

Present:
* FIU: Werner Boeglin
* JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni
Zihlmann

More on the Hall B Start Counter

Mark made a few more remarks about things the Youri Sharabian told us:
* When machining from a block of scintillator there will internal
stresses. It may have to be done as a two-step process if this is
attempted.
* Polishing is challenging. There was no hand polishing for the Hall
B start counter.
+ Molded surfaces have the best quality, better than if hand
polished.
* Cutting the scintillator too fast can lead to crazing. Likewise
trying to cut too much at a time.
* Wrapping the counters was difficult. Started with thermally shaped
Tedlar material.
* Rohacell does not come in large blocks so inner form support used
Plastifoam[?] machined out of a single piece, to about 1/4″ thick
* The outside foam was made of individual pieces, from a softer foam
than the inner foam. Woven cotton tape was wrapped around the
outside to secure everything.

Prototype News

McNeal promises to send their first sample today or tomorrow. They bend
the scintillator first and then machine the edges.

E&F Plastics had proposed to machine a the whole counter from a single
piece of scintillator. Samples were sent to them, but no word on any
progress. If McNeal does produce a satisfactory sample, Werner may go
back to this company.

When the sample for McNeal arrives it will be tested like previous
samples.

Eugene asked if we have the final dimensions for the counters. Werner
replied yes, to within 5 to 10%. The geometry is driven by largely by
the size and placement of the SiPM's on the read-out board.

Read-out design

Fernando is finishing work on the BCAL read-out for the beam test. He
will turn to work on the start counter soon.

Contract status

We discussed whether we should get started on this work with the design
in its current state, with some questions unanswered. Eugene thought
that we should aim for award of the contract at the beginning of the
next fiscal year which means we have to start getting the paperwork
moving now. Mark will send Werner a first draft of the documents to get
started.

Simulation

Simon asked about the current HDDS geometry. The change from 40
counters to 30 counters has not been put in yet. Same for the new
radial placement. Werner agreed to look into this.

Technical Design Report

Werner agreed to look at the start counter section.

Calibration and Alignment

Mark raised the issue of developing a conceptual design of how this
should be done. This involves
* identifying quantities to be calibrated
* calling out data that needs to be taken, both the type and the
amount
* sketching the analysis procedure
* noting dependencies on other detector systems

We will schedule a discussion for a future meeting.

Werner mentioned that he has had a plan to look into feeding LED test
signals into the counters somehow. This is largely a mechanical
problem.

Action Items

* Get sample from McNeal and test it. -> FIU team
* Write rough draft of contract documents and send to Werner. -> Mark
* Bring geometry in HDDS up-to-date. -> Werner
* Look at start counter section in the TDR. -> Werner

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"https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_19,_2012"

-- 
Mark M. Ito
Jefferson Lab (www.jlab.org)
(757)269-5295