GlueX Start Counter Meeting, April 19, 2012

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GlueX Start Counter Meeting
Thursday, April 19, 2012
10 am EDT
JLab: CEBAF Center, Room 326/327


  1. Announcements
  2. Review minutes from previous meeting
  3. Prototype Report
  4. Readout Design
  5. Contract Status
  6. Simulation

Communication Information

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2012-2Q on the JLab CUE. This directory is accessible from the web at .



  • 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.


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