Aug 11, 2015 Cal F250

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Video Conferencing Information

Meeting Time:

  1. To join via a Web Browser, go to the page [1] https://bluejeans.com/907185247.
  2. To join via Polycom room system go to the IP Address: 199.48.152.152 (bjn.vc) and enter the meeting ID: 907185247.
  3. To join via phone, use one of the following numbers and the Conference ID: 907185247.
    • US or Canada: +1 408 740 7256 or
    • US or Canada: +1 888 240 2560
  4. Upon connection all microphones are automatically muted. To unmute your mike on a Polycom or equivalent unit, enter *4. Unmuting on a computer is trivial as there is a microphone button than can be clicked.
  5. More information on connecting to bluejeans is available.

Participant Direct Lines

  • JLab Phone: in CC F326 is 757-269-6460 (usual room)
  • JLab Phone in CC L207 is 757-269-7084
  • Phone in the Regina Video-conference Suite is 306-585-4204

Action Items

List of issues:

  • Handling of pedestal subtraction for late pulses (leading to negative values) mark using quality bits
  • Why is the overhead in the file size so large (content is about 20%)? Header words and time references.

FA125's Useful Links

References

Tentative Agenda

  1. Announcements
  2. Action Items
  3. Updates
    1. Log Entry 3347898 Study of integration limits of BCAL signals
    2. Log Entry 3347605 Study of integration limits of FCAL signals
  4. Discussion
    1. Computation of baseline (long-term) pedestal
      • Goal is to have a robust average of many samples, eliminating outliers that could affect the mean.
  5. Any other business

Minutes

Attendees: Mark Ito, Manuel, Zisis (online); Mark Dalton, Elton, Matt, Beni, Sasha, Serguei (JLab);

  1. Announcements
  2. Action Items
  3. Updates
    1. Log Entry 3347898 Study of integration limits of BCAL signals
      • Mark Dalton summarized the work on determining the optimal start and end of the integration window using LED pulser data. The conclusion from this study is that integration between 2 and 13-17 samples after the threshold crossing gives the minimum width.
      • Mark Ito: Suggested that analysis of the window could determine the length of each pulse in the window and integrate samples within those samples. Elton: This would require to output the pulse length in the data stream for pedestal subtraction.
      • Mark Ito: Also stressed that variation in pulse shape (e.g. from scintillator response) could change the optimization.
      • Elton summarized a similar study as Mark's using pedestal data from R3281, but adding a simulated pulse. The general conclusions are similar as for Mark's study. However, this study also extended the window exploration to samples below crossing. It shows that for small pulses the minimum fractional width is indeed between about 2-12 counts (with threshold crossing sample=0). For larger pulses a similar minimum is reached, but there is also a broad minimum for starting before the crossing and integrating to beyond about 27 counts.
      • Conclusion: add an option to the firmware that allows definition of the integration window to start after the threshold crossing.
    2. Log Entry 3347605 Study of integration limits of FCAL signals
      • Matt summarized work by Manuel on the FCAL, studying an optimization similar to Mark's study (relative to the threshold crossing). The minimum width was found to be for samples 0 to 34.
      • In addition, the fractional minimum width was studied as a function of the start and end of the widow from the peak value (instead of the peak). The minimum width corresponds to the single peak value.
      • On the surface, it would seem that these two approaches are equivalent simply referenced to a different sample. The difference stems from the fact that the crossing sample can move relative to the pulse. The precise location of the peak relative to the threshold crossing varies by about one sample about 30% of the time, but by a much larger amount at the 0.1% level. The peak value is very stable.
      • The false threshold crossings should be alleviated by requiring consecutive samples to be above threshold.
      • Conclusion: investigate defining the integration window relative to the peak instead of the threshold crossing.
  4. Computation of baseline (long-term) pedestal
    • Goal is to have a robust average of many samples, eliminating outliers that could affect the mean.
    • Sasha explained the process for reading out pedestals using the secondary readout list.
    • When the system is so triggered, for example during synch events, all pedestals would be readout into the data stream as a different data type.
    • Synch events would be triggered at a predefined rate, e.g. at 1Hz.
    • The "pedestal values" would correspond to the sum of 2^N samples from a single event window.
    • Discussion followed as to how this could be used to track the pedestal baseline. Offline software would have to be developed to track the mean pedestal throughout the run. Mark Ito says that the hooks for doing this with ccdb exists, but is not implemented.
  5. Any other business
    • [Note added] Naomi has requested that we move our bi-weekly meeting to resume next week so that it will not overlap with the f125 firmware meetings. Our next meeting will be next Tuesday, Aug 18.
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