Time-of-Flight/Start-Counter Meeting, August 21, 2009

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Location, Time

Friday, August 21, 2009
3:00 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/2009-08 on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at https://halldweb.jlab.org/talks/2009-08/ .


  1. Minutes from the last meeting
  2. Time-of-Flight Status
  3. Start Counter Status
  4. Action Items


FIU: Seema Dhamija
FSU: Sasha Ostrovidov
JLab: Eugene Chudakov, Mark Ito (chair), Elton Smith, Simon Taylor, Tim Whitlatch

Review of Last Meeting's Minutes

We review the minutes from the August 7 meeting.

  • Last week Maurizio Bertoldi and Paul Eugenio came up from FSU and visited with Tim. They discussed mechanical support issues for the time-of-flight.
  • We briefly SiPM trouble seen in Hall B. Elton noted that those problems were after running with an electron beam and they may not be an issue for us. Dose studies should be done in any case.

Time-of-Flight Status

Sasha O. reported on recent progress. They have continued to work on the problem with one of the Hamamatsu not getting to 100% efficiency. Switching electronics does not change the behavior. If PMT's are swapped the problem moves with the PMT. Paul is trying to get another Hamamatsu H10534. They are also trying to measure the adc spectrum as the trigger counters are moved along the length of the counter. Amplification was suggested; something to try.

Start Counter Status

Seema gave us an update. The 3 mm thick scintillator is being tested is being tested with an LED pulser (120 ps pulse with 10 ns rise-time). A fine-mesh PMT is being used on one side, a SiPM on the other. The latter is coupled directly to the scintillator.

Studies with with cosmics rays will be done with a 2 cm wide trigger counter.

Werner has been making plots of of radiation length as function of polar angle for the current geometry.

recorded by Mark Ito