February 26, 2014 Calibration

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Meeting Time and Place

Wednesday January 15, 2013 at 11:00 AM. At Jefferson Lab, the meeting will be held in F326


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  1. Announcements
  2. Status Update
  3. Tracking
  4. Calorimetry
  5. Other systems
    • Photon Beam
  6. Simulations and Calibrations


Attending: Sean, Amiran (NU); Curtis (CMU); Simon, Beni, Mike, Eugene, Lubomir, Mark I. (JLab); Zisis (Regina); Richard (UConn); Justin (MIT)

  1. Status Update
    • Not much new since the Collaboration Meeting last week.
    • Sean proposed to have a few dedicated meetings for the purpose of integrating the constants into the reconstruction and simulation codes after the upcoming data challenge.
  2. Tracking
    • Naomi reported (in absentia) that she is generating the Garfield tables needed for the CDC time-to-distance relations.
  3. Other systems
    • Richard described the current ideas of what constants will be needed for the photon beamline detectors. There is a wiki page on this subject that he will provide a link to.
    • Discussion started with the tagger microscope
      • Each fiber is associated with a TDC and fADC250 channel. The TDC will need a time offset, and the fADC will need a gain factor and time offset.
      • The ADC pulse shape will be used to match fADC and TDC hits, and the ADC pulse height will be used to determine timewalk corrections for the TDC hits.
      • There are 120 channels in the microscope.
      • There should be 5 parameters per channel for the timewalk correction. The exact form of the correction is to be determined.
      • The high and low energy bounds for each channel in terms of the fraction of the endpoint energy should be stored.
      • The endpoint energy as determined in conjunction with the pair spectrometer should be stored.
      • The fixed array will need similar constants, it has 220 channels (?)
    • The active collimator is not needed for offline reconstruction
    • Pair spectrometer (PS):
      • The fine-segmented PS is purely hit-based, it checks for hits in coincidence gated with the coarse-grained PS.
      • The coarse-grained PS has 8+8 channels, each with an fADC250 channel and TDC channel, with the respective constants needed for each of them.
      • The gating threshold may also be needed for reconstruction.
    • Total absorption counter
      • 8 phototubes viewing a large block, each tube needs t0, gain factor, timewalk correction
    • Polarimetry will be discussed in the future.
    • The timing calibration of the tagger will first be done against the PS, then against the total absorption counter, and then with respect to the timing of the rest of the GlueX detector.
    • The ADC calibration of the tagger will be done using beam data with clean events (no pileup), in order to determine the timewalk corrections for the TDC.
    • Eugene asked about the detailed procedure needed to determine the energy range for the tagger channels. To first order, the high and low ranges with respect to the end point can be calculated by the information collected by Dan Sober, and the endpoint energy determined online. The calculation involves lots of information, e.g. the location of the magnet, the location of the focal plane, the tagger magnetic field maps, etc. This intermediate information could be stored in the CCDB, depending on how the calibration procedure is developed, but storing the derived per-channel energy ranges is more convenient for subsequent analysis.
    • Sean will derive a proposal for tables from this discussion.