Sep 21, 2010 Calibration/Monitoring

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Teleconference Time: 07:00 CST (Regina) /14:00 GMT+2 (Athens)

  • Direct Polycom point-to-point connection

Items for followup from previous meeting(s)

  1. None

Documents to Review

Tentative Agenda

  1. Winston cone versus Trapezoidal lightguides
  2. FCAL block plus Plexiglas test
  3. Review LED monitoring system


Attendees: Christina, George V., Pavlos (Athens), Zisis (Regina)

  1. Winston cone versus Trapezoidal lightguides: the current setup does not seem to be very robust: it includes a LED plus diffuser on one end of the baby cal and a PMT coupled on the other end via either lightguide using optical grease. Initial tests showed that trap/wico=0.8. A horizontal scan showed that max(trap)=max(wico), at different x positions. The setup needs to be improved, by ensuring that the diffuser system produces more uniform light.
  2. FCAL block plus Plexiglas test: these are in progress, and a horizontal position scan has been measured.
  3. Review LED monitoring system: see George V's May 2010 presentation as a reference.
    1. Improvements to current design.
      1. LED board: a) Reduce size to 603 format (18x6 mm2). b) Introduce ribbon cable.
      2. LPCM board: a) change USB interface to serial to interface with JLab slow controls. Requires reprogramming of microcontroller. b) Introduce 100-pin connector for easy detatchment of LED cables (32 can be accommodate on each LPCM board). Note that thet LPCM sends a TTL pulse, 4-4.5V and 15ns risetime.
    2. Issues to be address by Calorimetry Group.
      1. LED+LPCM or laser system?
      2. Type of LED?
      3. Channel count: Does every channel of the BCAL (and TOF) need a LED?
      4. Geometry: Final LED board size? Where should the LED's be placed? Board directly on LG (works for trap design)? Glue LED to LG (probably Wico design needs this)? Where to threat cable from LPCM to LED? Where to put LPCM (piggy back on SiPM board -- RF issue, or in separate box near BCAL, or in electronic racks -- long cables, cost issue)?
      5. Mass production in robotics facility (like IU's)?
      6. Slow controls interface and software. Feedback system to adjust LED bias (include temperature sensor from SiPM?) What is needed for all this?
      7. Dynamic range of SiPMs; can we flash both sides simultaneously, or do we adjust LED biases for near vs far PMT.
    3. How to proceed
      1. Athens will write a construction MOU, which will include R&D and a prototyping plan.
      2. Once LED configuration and numbers are settled, an updated quotation will be requested. For example, to instrument all BCAL LEDs, 130 LPCMs are needed each with 32 LEDs, for a total of 3840 LEDs.