GlueX Start Counter Meeting, April 17, 2014

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GlueX Start Counter Meeting
Thursday, April 17, 2014
10:00 am EDT
JLab: CEBAF Center F326


  1. Announcements
  2. Electronics
  3. Review minutes from previous meeting
  4. Detector Construction Status
  5. Support Structure Construction Status

Communication Information

We will use BlueJeans for this meeting.

  • To join or start the meeting, go here.
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    1. Dial: or
    2. Enter Meeting ID: 556286544 -or- use the pairing code
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    1. Dial-in: +1 408 740 7256 or +1 888 240 2560 (US or Canada only) (other phone numbers)
    2. Enter Meeting ID: 556286544


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2014-2Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Eric Pooser
  • JLab: Fernando Barbosa, Eugene Chudakov, Mark Ito (chair)

You can find a recording of this meeting at here.


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.


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 (PDF, 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.