GlueX PID Meeting, October 1, 2010

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Location, Time

Friday, October 1, 2010
2:00 pm EDT
JLab: CEBAF Center, Room F326/7
ESNet: 8542553
EVO: direct meeting link
Conference Group: 800-377-8846, participant code: 77438230
Slides: talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2010-10 on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at .


  1. Announcements
  2. Minutes from the last meeting
  3. Time-of-Flight
    1. Prototype Status
    2. Calibration system
    3. Mechanical interface to support structure: real estate planning
    4. MOU status
  4. Start Counter Status
    1. MOU plans
  5. Target
    1. Refrigerator update
    2. MOU status
  6. Action Items



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

TOF Prototype Studies

Sasha reported on progress at FSU.

Time Resolution

He has done new time resolution tests with the new Hamamatsu PMT's. To do this back to use the CAEN constant-fraction discriminators. With the new tubes at two voltages:

Voltage (V) Resolution (ps) Comment
1750 140 recommended voltage
2000 114 maximum voltage

Compare this to the previous best measurement with the old Hamamatsu tubes at 2000 V of 124 ps. All resolutions quoted are for (t2−t1)/2.

These tests were done with Tyvek wrapping. When ESR was tried, at the higher voltage, the resolution was 112, not much improvement. Tests were also done with a 50-50 signal split. Resolution came out at 116 ps, very little effect. Using the new JLab leading edge discriminator, without any time-walk correction, gives 180 ps.

Beni suggested that Sasha make an estimate of the PMT lifetime at various voltages. He noted that lifetime is usually quoted by the manufacturer in terms of total charge sourced by the tube.

They are using the new, triggered data acquisition system now. The next step is to get the new lab room ready to accept the large trigger paddle configuration.


Fernando Barbosa has sent 2 splitters and 2 inverters to FSU for testing. They have not arrived yet.


Paul Eugenio sent us a new version of the MOU, incorporating language suggested by FSU legal staff. Elton has prepared a new draft, with the new language, and will send it along to Glenn Young and Allison Lung.