GlueX TOF Meeting, July 26, 2016

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GlueX Time-of-Flight Meeting
Tuesday, July 26, 2016
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
  2. Review of minutes from the previous meeting
  3. PMT order
  4. Cosmic data
  5. Calibration Updates
  6. NIM paper



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2016 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Sasha Ostrovidov
  • JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site.

Review of minutes from the previous meeting

We went over the minutes from July 19. No significant comments.

PMT order

Ardavan Ghassemi of Hamamatsu sent us an email cautioning us that the current PMT model used in the TOF will be discontinued as some point soon. He proposes a replacement model and sent along a data sheet for the R13435. The new tube has a diameter about 1 mm greater than the old.

Cosmic data

Beni led us through his plots:

  • looking at signal amplitude vs time difference for 1350V Amp vs dt 1350V paddle11 plane2.jpg Amp vs dt 1350V paddle11 plane2 zoom.jpg
  • The flash250 ADC op-amp signal inverting input causes a baseline shift that feeds back to the input to the leading edge discriminator resulting in a miss match between threshold setting and actual threshold.
  • other examples of amplitude vs dt paddle 18 plane 1: Amp vs dt 1350V paddle18 plane1.jpg
  • or paddle 20 plane 1: Amp vs dt 1350V paddle20 plane1.jpg
  • or paddle 20 plane 2: Amp vs dt 1350V paddle20 plane2.jpg
  • and the same PMT but 100V higher at 1450V: Amp vs dt 1450V paddle20 plane2.jpg

The DC shift in the baseline at the discriminator from the FADC can be as much as 35 mV and depends on the FADC channel. We will need to have channel-by-channel discriminator settings, especially when running the tubes at lower gain.

The next step is to try and look at time resolution at new reduced voltages.

Next Meeting

We will meet again in a week.