Dec 8, 2008 Calorimetry

Time: 11:15 ET.

• Phone:
  • +1-800-377-8846 : US
  • +1-888-276-7715 : Canada
  • +1-302-709-8424 : International
  • then enter participant code: 39527048# (remember the "#")

Items for followup from Nov 24 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.
   • Check what configuration (thresholds, step sizes, stack? parameters for secondaries, etc) is being used for the Hall D simulations (Regina)
3. Report on the Bfield components in the region of the Bcal reaout (JLab for next meeting).

Documents to Review

1. Calibration/monitoring update Athens (old version): Media:APD_vs_tube_linearity.ppt
2. Calibration/monitoring update Athens (updated): Media:APD_vs_tube_linearity2.ppt
3. Calibration/monitoring update Athens: Media:Threshold.ppt

Tentative Agenda (Emphasis is Calibration)

1. Announcements
2. Calibration
   • Progress on filling in the Calibration Specification Table.
3. FCAL Update
4. BCAL
   1. Testing of fibers with SiPM readout and Sr90 source (Beni)Talk
   2. Lead Specification (Elton)
   3. Magnetic Field Update (JLab)
   4. Other updates
      1. if time: Resolution studies
5. Any other business

Minutes

Attending: Athens: George Voulgaris, Christina; JLab: Tim, Fernando, Beni, Elke, Elton; FSU: Alex; UofR: Blake, Zisis, George, Andrei; IU: Matt (please add others if present)

1. Announcements
   • Elton will attend Sendai08 to present some Hall B data and will take advantage of trip to visit Kuraray.
2. Calibration
   • No updates on the calibration table requirements. Alex indicated that FSU will review the table and give feedback as testing on TOF detectors proceeds.
   • George V. reviewed the two posted presentations, one on pmt and APD linearity and the second on LED thresholds.
   • First, radiated noise from laser reduced using a Faraday cage. Remaining background levels in APD spectra (50 mV) reduced to 2 mV using various stages of shielding.
   • Linearity of APD established by comparing to LED. Comparing pmt to LED, determined range of "overlinearity". After correction for this non-linearity, the measured response ratio between pmt and APD is 3.3/3.2.
   • Conclusion: APD is useful device for calibration. In comparisons with PMT, Elke cautioned that one is comparing different active areas as well as different gains.
   • Christina: Main goals at present ar to compare linearity and time stability.
   • Zisis: Inquired about future measurements with SiPMs? Yes, that is the plan. Also, the fine mesh PMT will be studied.
   • For LEDs, additional studies are required on temperature and time stability
   • Elke: Should review existing literature and other detectors as basis for planning design. Christina, said that indeed a review of literature has been conducted and most systems either use lasers with optical benches (expensive), or moving toward LEDs, which they are presently investigating.
   • Christina: most of the laser tests have been completed, they are now concentrating on LED tests.
   • Elton asked what were the driving inputs that are required to design the calibration system. George V.: dynamic range is one of the major factors. Fernando: His experience is that LEDs vary considerably in output (even from the same batches) and recommended testing a larger sample to investigate variation in light output.
3. FCAL Update
   • No update
4. BCAL
   1. Testing of fibers with SiPM readout and Sr90 source (Beni)Talk
      • Summary of light output at three differenct distances using pmts and SiPMs for Bicron and Kuraray fibers. All summarized on wiki. Beni will consolidate into a GlueX-doc note and post on the portal.
      • Andrei inquired about the subtraction of non-source triggers in the SiPM measurement. Under question was the ratio of cosmic-ray triggers vs. pmt dark rate. Beni indicated that the correction was only 20%, so it could not affect the conclusions very much. However, it will be quantified further.
      • Zisis asked about the differences between this measurement and the spectophotometer measurements. This is likely due to the assumed PDE function for the SiPMs (about 13%) used in the interpretation of the spectrophotometer measurements.
   2. Lead Specification (Elton)
      • There has been an iteration on the Pb spec with George and Zisis. A close to final spec has been posted on the portal. Tim will get feedback from vendors about the difficulty in supplying specific lead sheets sizes.
5. Nex time:
   1. Magnetic Field Update (JLab)
   2. Resolution studies