GlueX TOF Meeting, July 17, 2014

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GlueX Time-of-Flight Meeting
Thursday, July 17, 2014
10:00 am EDT
JLab: CEBAF Center, F326


  1. Announcements
  2. Review of July 3rd Meeting
  3. Review of July 8 DAQ Planning Meeting
  4. Installation Update (Sasha, Aristeidis)
  5. Meeting Schedule (all)



Talks can be deposited in the directory /group/halld/www/halldweb1/html/talks/2014-3Q on the JLab CUE. This directory is accessible from the web at .



  • FIU: Hussein Al Ghoul, Paul Eugenio
  • JLab: Chuck Hutton, Mark Ito (chair), Sasha Ostrovidov, Aristeidis Tsaris, Beni Zihlmann

Installation Update

Sasha gave the report.

Scaler Read-Out

  • Discriminator-based scaler read-out is working now. Rates have been measured with the PMTs at 1250 V and a 30 mV threshold in the discriminators. See an example below.

Tof scalers 1250V snapshot1.png

  • Based on these scaler rates, there appear to be no light leaks in the system.
  • There were two channels with zero rate due to cables badly plugged-in. These have been fixed.
  • The correspondence between HV channels and discriminator channels was checked again yesterday using the HV GUI and scaler read-out. Sasha would like to repeat the exercise for the FADCs. We thought that the FADC-based scalers would be good for this.

Cosmic Data Taking

Sasha showed three events (see below). Bars colored in yellow indicate FADC hits, red dots show position determined from end-to-end time differences from the TDCs. Note that the TDC times have no calibration applied.

Tof view2.png

Tof view1.png

Tof view3.png

Yesterday a long run of 20 k events was taken. It took about half and hour to take the data. The average event size is 80 kB.


Over the course of the past week or so several problems were found and fixed (mostly).

  1. Last week an FADC with a bad bit was replaced. The new board had an old version of the firmware and did not play well with the data acquisition. A firmware upgrade fixed the problem.
  2. The HV GUI was in a frozen state that made it appear that the voltages were on when in fact they were not.[1] Once this was realized it was fixed by restarting the IOC.
  3. At one point during calibration runs to set pedestals, the DAQ started crashing. This turned out to be due to a long configuration file name.
  4. Cables are plugged into the splitters in a haphazard way. Although the front-panel connectors are labeled "in", "A", and "T", these labels are not always respected. Since the splitter circuit is passive and three-fold symmetric this has no effect on operation but is confusing when trying to debug problems.

Near-Term Tasks

  • Sasha and Aristeidis will start a program to raise the voltages to their nominal values (determined on the bench at FSU) in small steps, checking discriminator rates as they go.
  • There is one channel with a dead ADC channel in cosmic data. This channel reported a nominal value in the pedestal runs previously. This problem is not understood at present.
  • Paul asked about implementing a system to monitor scaler rates independent of the DAQ state. The EPICS read-out of the discriminator scalers should be able to do this when it is implemented.

Action Items

  1. Ask about the status of the FADC scalers.
  2. Track down the configuration file name bug.
  3. Implement scheme to avoid confusion about HV status.
  4. Get the splitters cabled consistently.
  5. Ask about DAC value read-back capability on the FADC-250.
  6. Ask about the status of EPICS read-out of discriminator scalers.

Meeting Schedule

We decided to meet weekly on Tuesdays at 10 am. Every other meeting will be focused on issues with installation/commissioning in the Hall.
  1. "The GUI lied brutally to our faces."