Run 12 pp510 SpaceCharge & GridLeak status

Run 12 pp510 SpaceCharge & GridLeak status as of August 1, 2012:


  • SC & GL calibrated for all of the data except days 85-86 (due to altered ZDC operations on those days). Uploaded to database.
    • Days 85-86 could be calibrated within a few days, but we decided to wait on other studies (listed below)
  • Results of calibration challenged on observed luminosity dependence of BeamLine calibration results
  • Two-pronged approach:
    • GridLeak dependence on Anode HV calibration (work was already planned)
      • Calibration work finished, but new questions arose on QA checks (presented at last week's S&C meeting)
        • Observed signed DCAs at primary vertex exceeding 1cm for some sectors!
      • No breakthroughs yet, and thus no time estimate on resolving this
        • One idea for workaround being tested (skipping first padrow as done in Run 6 data)
        • Turning off sectors is an open possibility (has precedent)
    • Studying charge distribution in the TPC
      • Student getting up to speed on the task who will do future work on SC & GL
      • Preliminary results do show some luminosity dependence of radial shape, but no clear asymmetries in phi (i.e. no obvious connection to sector-dependence)
      • Quantification of observed dependence and subsequent impact remains to be done (need to answer the question of significance of what is seen), and may take a couple more days to finish
      • Options:
        • If nothing significant found, so nothing to be done and we move forward with production
        • If something significant found, would require significant work on re-calibrating the data (weeks, almost certainly impacting delivery for DNP). Significance would need to be quantified for physics deliverables and the decision on whether that's acceptable to analyses would be asked to decide whether to proceed on a production without improvements or not.
  • Conclusion: a couple tasks ongoing which would give us a decision point by early next week on whether and how to proceed.

UPDATED CONCLUSIONS from today's S&C meeting:

  • No major re-calibration is going to occur within the next week in time for a preview physics production, so we should proceed with calibrating days 85-86 as it stands, and prepare for beginning the production ASAP.