Apr 2, 2009 Calorimetry

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Teleconference Time: 4:45 p.m. EST

  • Phone:
    • +1-800-377-8846 : US
    • +1-888-276-7715 : Canada
    • +1-302-709-8424 : International
    • then enter participant code: 39527048# (remember the "#")

Items for followup from previous meeting

  1. Resolution studies (Blake)
    • Develop criteria for evaluating resolution studies
    • Study impact of inactive material at the end of BCAL on acceptance.
    • Check what configuration (thresholds, step sizes, stack? parameters for secondaries, etc) is being used for the Hall D simulations (Regina)
  2. Review options for import/export to Chile (loans, donations, transfers, etc.)
  3. From stand-alone MC, or previous notes, collect the distribution of photons expected for numbers of photons for various showers (especially at low energies, e.g. 50 MeV - 200 MeV) and typicall positions (i.e angles) along the calorimeter. (Andrei).
  4. JLab to have some informal discussions on various cooling concepts to be presented at the next meeting.[http://www.jlab.org/~huttonc/siPM_layout.ppt cooling}

Documents to Review

  1. Fiber Summaries (JLab)
  2. Fiber Measurements
  3. Simulation of BCAL Threshold GlueX-doc-1231

Tentative Agenda

  1. Announcements
  2. FCAL Update
    1. FCAL Magnetic Shield Design
  3. Simulations
    1. Simulation of BCAL Threshold: GlueX-doc-1231 (Matt)
    2. BCAL Dark Hits (Matt)
      1. Resolution Dependence on Dark Rate
      2. π0 Peak for Different Dark Rates
  4. BCAL Update
    1. Preparations for construction
    2. Results of Fiber Tests
      1. Kuraray Fibre Tests - Regina - updated (Blake)
      2. Kuraray No of pe - April 2, 2009 - updated (Andrei, Kathryn)
    3. Cooling of BCAL Readout
  5. Review of Action Items


  1. Attending: JLab: Beni, Elton, Fernando, Eugene, Tim, FIU: Werner, UofR: Zisis, Blake, Kathryn, George, Andrei; IU: Mijahlo, Brad, Claire, Matt.
  2. Cooling of BCAL Readout [moved forward due to accomodate Tim's schedule]
    • Tim presented a preliminary concept for cooling the SiPMs GlueX-doc-1233 DRAFT Cooling Concept
    • Based on JLab informal discussions.
    • Idea is to directly cool the sensor via Peltiers to 5deg C with a cooling circuit at room temperature to remove the heat generated by Peltier (~1.5 Watt/channel).
    • SiPM geometry based on SensL ceramic design which allows cooling sensor directly by offsetting electronics via long pins.
    • Peltier junction and sensor would be potted to prevent condensation on sensor. Potting is needed to have sufficient insulation to confine cold area.
    • Should provide a concrete basis for further discussion.
    • Matt: Mentioned that CLEO had good success with the following scheme for cooling their drift chamber electronics: Fill space with (dry) N2. Use polyethelne tubing with cooling liquid (PF200) to cool N2. System was robust and inexpensive.
    • Zisis: individual mounts or bars across several SiPM cooling plates will be decided based on how accurate the machining and alignment can be done (of all components). A set-screw system can be used in the case of bars across 4 SiPMs (in the same row) to individually apply pressure to each SiPM all the way to its Winston Cone/cookie interface.
  3. FCAL Update
    1. FCAL Magnetic Shield Design
      • New rectangular magnetic shield mechanical prototype is under development. Allows more space for electronics
      • This gets the design away from the flex boards which were fragile and costly
      • New design would have 3 PC boards: one for control, one for HV and one with connections. The HV part was the lest reliable. This design would ease maintenance of that particular board.
      • Elton: Check to make sure that there is sufficient space between grounds and (negative) HV. Gradients can lead to small ion mobility in the glass and deteriorate photocathode. Will try to dig up some references.
    2. John has finished glass support drawings and sent them to Tim.
    3. Would like to see the results of field calculations for new design to evaluate impact on pmt performance.
  4. Simulations
    1. Simulation of BCAL Threshold: GlueX-doc-1231 (Matt)
    2. BCAL Dark Hits (Matt)
      • Resolution Dependence on Dark Rate
      • π0 Peak for Different Dark Rates
      • Adjusted threshold settings for an occupancy of 5%.
      • Evaluated resolutions based on realistic GEANT simulation and reconstruction.
      • There are two effects due to increased rates: 1) dark rate increases and 2) threshold are increased. Both affect resolution.
      • These studies show that our nominal goals of 40 MHz affects resolution only slightly, but rates of 160 MHz have substantial impact on resolution and reconstruction. These studies support our goals for PDE/dark rate goals.
      • Note to Blake: It is likely that the calibration will change at low energies and further studies will require a re-calibration.
  5. BCAL Update
    1. Preparations for construction
      • Small contract will cover the production prototype (49th module)
      • Contract will include construction manager as well as fabrication of 48 modules
      • Purchase Reqs are nearly ready for submission.
      • Hard-date of May 1st give to UofR divisions to have construction space ready (swaging space is exempt from this as a fallback exists).
    2. Results of Fiber Tests
      • Elton: First article fibers have been approved and Kuraray has been directed to proceed with production. Even though there are systematic differences between JLab and Regina measurements, all results point to Kuraray satisfying our specifications. See File:Hamamatsu pages.pdf Guidelines from Hamamatsu
      1. Kuraray Fibre Tests - Regina - updated (Blake)
        • More fibers have been measured. Attenuation lengths are uniform between samples (~450 cm) and reproductible, but higher than those measured by Kuraray and JLab.
      2. Kuraray No of pe - April 2, 2009 - updated (Andrei, Kathryn)
        • Andrei described procedure for the measurement of absolute number of photoelectrons. 90Sr source placed at midpoint of fiber, 200 cm away from a SiPM on one side and 200 cm away from calibrated pmt on the other. PMT was used as trigger and SiPM spectra was evaluated. Result was a number of about 5.5 p.e. in response to the source.
        • The SiPM spectra was corrected for triggers unrelated to source.
        • The threshold of the PMT on the extracted number of photoelectrons was studied and reduced the number by about 0.3 p.e.
        • Zisis will send a reference to similar fiber studies by COMPASS.
    3. Note: Box of fibers bound for Regina was crushed. Half of the samples from the box were shared between JLab and Regina. There is agreement that the fibers in the damaged box were not affected.
  1. Review of Action Items