Time of Flight Meta Meeting

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Location, Time

Thursday, April 2, 2009
2:45 pm EDT
CEBAF Center, Room F326/327
EVO: direct meeting link (we will try this first)
Conference Group: 800-377-8846, participant code: 39527048
ESNet: 8542553


  1. 12 GeV Project schedule and GlueX time-of-flight
  2. mechanical engineering support
  3. current status of effort
  4. need/schedule for future meetings


JLab: Eugene Chudakov, Mark Ito, Elton Smith, Alexander Somov, Simon Taylor, Beni Zihlmann
FSU: Paul Eugenio, Alexander Ostrovidov

Schedule and Budget

  • Eugene mentioned that the PED phase of the 12 GeV Project is over, yet there are still some items on the time-of-flight (TOF) that are a bit behind. These include developing designs for the scintillators, bases, support structure, splitters and an integration plan.
  • Under the construction phase there is procurement of scintillators, light guides, power supplies, PMT's, cables, etc. along with assembly and testing.
  • There is 620 k$ allocation for construction.
  • Construction is scheduled to start in FY12. As such it cannot be pushed forward with stimulus money.
  • The schedule can be found among the pre-brief material for the installation review.
  • Funds for initial studies were tranferred from the UPV to the TOF.
  • The schedule has lots of manpower for assembly and testing during construction.
  • There is 113 k$ in the budget for the calibration system for the TOF alone.
  • There is 21 k$ budgeted for materials for the support structure.

Mechanical Engineering Support

  • Paul has two machine shops available at no cost at FSU. They have simple design capabilities, but probably cannot produce the formal design drawings needed for the final design.
  • Elton mentioned that those resources were probably sufficient to usefully iterate and test designs and then a mature version could be produced at JLab.

Status of Effort

  • The machine shop at FSU is building light guides now. Paul hopes to have a piece by tomorrow.
  • Paul is working on the draft of the MOU. He is modeling it on the one from Carnegie Mellon. He notes that there are expectations outlined for both the university and the Lab. He will need to consult with JLab folks on the proper division of labor for the TOF. Paul will contact Mark if he has further questions.
  • Nominal scintillator dimensions: 6 cm x 1 in. (you can't make this stuff up.), though wider scintillator was purchased for study.
  • The light guide design is complicated by the fact that the PMT's with their shields will not fit in straightforward arrangement. Two solutions are being considered:
    1. bend light guides "left and right", the default solution
    2. construct the array with wider bars. This might affect the time resolution and must be studied.
  • For initial testing, a straight trapezoidal light guide is being produced now.
  • There was a problem obtaining 2 in. thick UVT from Elgin.
  • IU's fish-tail light guide design has not been tried yet.
  • IU studied counters with the PMT coupled directly to the scintillator. FSU wants to study effect of having a light guide.
  • Eugene asked about which PMT will be used.
    • Paul has two Hamamatsu tubes in hand, a H10570 (8 stages), and a H10534 (10 stages). These are $810 each including a base with Zener diodes and a μ-metal shield for quantities of 100 or more
    • He also has two Photonis tubes: an XP2020 (12 stages) at about $1500 and a XP20V0 (8 stages) at $800, for the tube only in both cases. A base is $250 extra.
    • Transient time spreads among these tubes are comparable.
    • There is 190 k$ allocated in the budget for tubes including bases and shields. 200 are required.
    • Sasha mentioned the idea of getting used PMT's.
      • HERA-B had Hamamatsu PMT's for their shaslik calorimeter; timing characteristics not known.
      • BABAR seems to be holding on to their stuff at present.
  • There will have to be a decision made on using constant fraction vs. leading edge discriminators. Beni noted that the current plan includes TDC's and ADC's for each channel. Rate issues should be studied.
  • Elton brought up the idea of having scintillators which are displaced but slightly overlapping to simplify the light guide design. It might have the added benefit of closing "cracks" between the counters.
    • As mentioned before FSU is looking at wider than nominal counters. This would be helpful for such a design.
    • Paul mentioned a previous study looking at the geometric acceptance of the total array. He thought that a re-examination of the data might tell us something about what angles of incidence to expect for the TOF. He will try to do that.
    • Beni pointed out that an overlap design will have trajectories that have a very small path length in scintilator.

Next Meeting

We agreed that the meeting was useful. We will try to meet again in two weeks. We will also try to incorporate planning for the start counter into the agenda.

recorded by --Marki 17:58, 2 April 2009 (EDT)