Nov 24, 2008 Calorimetry

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Items for followup from Oct 27 meeting

  1. Updates on Calibration Specification Table.
  2. Resolution studies (Blake)
    • Develop criteria for evaluating resolution studies
    • Study impact of inactive material at the end of Bcal on acceptance.
  3. Add F100 rad hard glass to simulation. - New graduate student has been assigned this project.
  4. Add roadmap for Bcal Roadmap to wiki (Elton)
  5. Check what configuration (thresholds, step sizes, stack? parameters for secondaries, etc) is being used for the Hall D simulations (Regina)
  6. Updated schedule with new Fcal procurement dates. (Elke will send this to Matt)
  7. Report on the Bfield components in the region of the Bcal reaout (JLab for next meeting).
  8. Updated drawings of Bcal modules (including O-ring) for discussions. Tim will see if that can be fitted into designer tasks.

Documents to Review

  1. Calibration/monitoring update Athens: Media:APD_vs_tube_linearity.ppt
  2. For components of the magnetic fields see GlueX-doc-912, Figures 9 and 11.
  3. APD Material for Serguei's presentation: [1],[2],[3]

Tentative Agenda

  1. Announcements
  2. Calibration
  3. FCAL
    • Report of timing studies with pmts and time calibration (Jake Bennet) [PDF slides]
    • Approximations of the sqrt( -ln( x) ) function for the timing algorithm (Mihajlo): [T50 expansion]
    • Discussion with C. Cuevas & Co.
  4. BCAL
    1. BCAL readout
    2. Resolution studies
    3. BCAL Construction MOU
    4. SiPM progress
    5. Readout
      • Review of use of APDs for readout -- see material in 'Documents to Review' above (Serguei)
      • Magnetic Field Update (JLab)?
  5. Any other business


Attending: Fernando, Hai, Ben, Ed, Chris, Elke, Serguei, Beni, Elton (JLab), Claire, Mihajlo, Jake, Matt (IU), Will (Chile), Christine (Athens), George, Andrei, Blake, Zisis (Regina)

  1. Followup items:
    1. No new updates to Calibration table, but this will be revisited in December.
    2. Resolution studies: see Blake's update below.
    3. F100 glass: in progress.
    4. Roadmap looks fine. Zisis and George went over it and have nothing to add.
    5. Hall-D simulations and configuration: in progress.
    6. FCAL procurement schedule: Matt and Elke are working on this offline.
    7. BCAL BField report: postponed to Dec 8 meeting.
    8. BCAL drawings: special meeting schedules for Dec 2.
  2. Calibration/Monitoring System: (see above link for PPT presentation). Christine gave us the highlights.
    1. Much work has been done in trying to suppress noise from the IU laser (used at 2 pulses/sec). The laser is also somewhat unstable in intensity (the Burle 8575 PMT also); Matt confirmed this from E852 experience, and added that the beam spot also tends to walk. Matt will try to dig up more info if available.
    2. Ratio of central/side hole for PMT is ~4 and for APD ~3. Non-linearity at high light output was seen. Light has a wider pulse for the central hole.
    3. Temperature instability is also a concern.
    4. Plan to use a FM PMT instead of the Burle one for better linearity.
  3. FCAL
    1. Jake's presentation on FCAL resolution studies (see slides above):
      • LED used; channel 8 was held constant on p.11 (note its fluctuation in the right panel).
    2. Mihajlo's presentation on approximations to the FADC timing algorithm (see slides above):
      • Delta_T_50 black curve is the distribution with bifurcated Gaussian fit; p.4. oscillations are ≤ 2% but he will try to do better.
      • Discussion with Chris' crew: subject was programming into the FPGA sqrt(-lnx) as a lookup table versus an approximation. Studies need to be done (6 months from now based on the time table) to see which method is more efficient. It is a chip memory vs calculation issue. Mihajlo suggested another option: store three values (peak amplitude, x1, x2) and analyze the timing offline (reduces chip load). IU aims at a NIM article from their FADC work.
  4. BCAL
    1. Blake's Resolution studies (see sldies above)
      • He is in his initial step on these studies and is getting a handle on how the quantities in the ROOT tree relate to each other; these plots show photons hitting either calorimeter. Elke suggested that the study focus initially on both photons in the BCAL.
      • George reported on the construction MOU corrections; they will be sent to JLab soon. Also, the UofR is nearing the final decision on the overhead rates.
      • George reported that Kathryn is continuing the SiPM tests with the TIA boards. The pulses look nice without overshoot but the gain is too low, and measurements will continue using an external x10 amp.
      • Alternate readout option: APD (see Serguei's slides from above). The energy resolution (5%/sqrt(E)+1% looks too high for such a device. The APDs need temp stabilization using a water chiller. QE is very high (80-90%). Gain is quite low. A comparison table to other readouts is at the end of his slides. APDs for BCAL would have to deal with their noise and low gain. Elke suggested buying such units next year to run tests on them.
  5. Next meeting on Dec 8 dedicated mostly to Calibration/Monitoring.