Nov 23, 2010 Calibration/Monitoring

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Teleconference Time: 07:00 CST (Regina) /08:00 EST (Jlab) / 15:00 GMT+2 (Athens)

  • EVO meeting

Background information

Tentative Agenda

  1. Go over goals/objectives of Monitoring system.
  2. Christina/George and I are not convinced it is easily doable or practical.
  3. Start updating the system requirements table and discuss LED plan/options/upgrades.
  4. We need to make a proposal to the working group about these three items and if agreed upon plan how to proceed (via construction MOU with Athens, etc).


Attendees: Christina (Athens), Elton (JLab), Zisis (Regina)

  1. Zisis conducted three two-way calls, with Christina, then Elton, then Christina again.
  2. Elton emailed issues to discuss:
    1. SiPM non-linearity - We should have a system that can check the linearity of the sensors. A method to do this is have 2, 3 or 4 LEDs illuminating each channel which can be fired separately or in unison. The sum to single LEDs should match the response to multiple LEDs firing at the same time. I will call this an LED source.
    2. Temperature stability of SiPMs - Both LEDs and SiPM have temperature dependences, so the monitoring system dependence should be isolated from the SiPMs. This points to a monitor system with a source of several LEDs which are located outside the enclosure with the SiPMs with several fibers that run into the box and get connected to individual light guides. That way the temperature of the LED source can be monitored at a few places and those places will likely be in areas with different temperature characteristics than the SiPMs
    3. Sums of SiPMs - Since we are summing 3 to 4 SiPMs into a single electronics channel, it would be useful to be able to pulse SiPMs going into a sum separately from the others. This suggests having at least 4 LED sources four each end of the Bcal, so that it is easy to pulse each SiPM in the sum separately.
    4. Opposite ends of the Bcal - If the LED source has sufficient number of LEDs or power, one can think of pulsing this at ten times the intensity of the near side to investigate the response to the far side.
    5. General comment on individual LEDs for individual light guides: This arrangement allows for individual SiPMs in a sum to be pulsed, but lacks many of the other characteristics that would make the monitor system useful.
  3. It was agreed that we would think about these issues and the background links above, and arrange for another phone or video conference next week to move ahead. The goal is for the three of us to come up with a proposal for the Monitoring System to take to the Calorimetry Group.