Difference between revisions of "GEM Meeting/20190125"

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* Tao: GEM analyzer/decoder concerns and data characteristic investigations
* Tao: GEM analyzer/decoder concerns and data characteristic investigations
* Test lab setups
* Simulation of SLAC data to compare

Latest revision as of 16:03, 25 January 2019

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  • Tao: GEM analyzer/decoder concerns and data characteristic investigations
  • Test lab setups
  • Simulation of SLAC data to compare


  1. Tao - SLAC analysis update, quantifying differences between QDC and GEM multiplicities, and GEM pedestal studies (ask Cameron for SLAC test beam user account on ELOG):
    • Verified that all data is complete in QDC and GEM (no missed events in one or the other)
    • Cross checked Decoder with event counter
      • Two data words encoding event number added to decoder to double check event counts
        • QDC index starts at 0, GEM MPD index starts at 1, so we expect an offset by one in these event counters
    • Trying to find another way to cross check the analysis steps
    • GEM multiplicities appear to be systematically ~15% lower than QDC multiplicities
      • There is a clear correlation of QDC mult to GEM mult, though probably the GEM efficiency is too low and pedestals are maybe an issue too
    • There appears to be a bimodal behavior of events - events with a clear spike in the GEM and low RMS, and events with no clear spike in the GEM and high RMS (and often a large multiplicity in the QDC)
      • It would be nice to see if separating these two kinds of events and looking at just the low RMS ones would clean up the correlation of multiplicities between GEM and QDC
    • Cross-talk slides are also uploaded in the same entry as the pedestal studies entry
  2. Bryan: parameter in the APV config files
    • Speed set to 350
    • ADC clock phase needs to be adjusted to remove reflections for large signals causing large RMS's
      • This parameter is for MPD vs. APV clock offset - Dustin set it at 12 at ISU, unknown at SLAC, we can replicate in TEST lab
  3. Dustin: CAD files for SLAC test beam, for use in determining simulation geometries and generating images
  4. Chandan: Cosmic run in TEST lab
    • I2C issue causes error in 1/3 of events
    • QDC doesn't see the gates, and this happens even though you would expect it not to with low rate cosmics
      • Including a QDC busy veto on MPD reading prevented this from being an issue at SLAC
      • Cosmic running shouldn't actually be busy
        • Diagnose this by looking for timing de-synchronization in cosmic runs, potentially due to bad noisy grounds
  5. Chandan: DAQ setup from ISU does not have MPD reading problems that SBU DAQ witnessed at SLAC
  6. Bob: Devi can use cubicle 12 next to Bob's 11 in TEDf lab space
  7. Dustin: Will build the second low voltage power supply with new parts that have arrived
  8. Chandan: Can decode the cosmic QDC and GEM data just fine, no decoding errors, but one of the QDC sensitivity settings (probably low) cannot see signal
  9. Brady: Has gotten Quartz QDC data in his copy of the analyzer
  10. Joey: Sees the same QDC/MPD mismatch Tao sees
  11. Carlos: Using poissonian multiplicity algorithm in qsim simulation gets a good fit to data
    • Still needs to get the PMT cathode sensitivity curve from the vendor
    • Can run the simulation for longer than the data run that was taken, and can probably merge multiple similar runs together
  12. Tao: see run 411 tracker event 36 - maybe one sample is missing, since the sides of the GEM are much lower falloff edge or shoot up higher edge - maybe this is because a sample is missed (or artificially 0)


Chandan, Cameron, Seamus, Brady Lowe, Bryan Moffit, Dustin, Devi, Joey McCullough, Ryan Richards, Siyu, Tao, Carlos