Feb 11, 2010 Readout

Teleconference Time: 11:00 a.m. EST

• ESNET and EVO session
• Phone in CC F326 is 757-269-6337
• Phone:
  • +1-800-377-8846 : US
  • +1-888-276-7715 : Canada
  • +1-302-709-8424 : International
  • then enter participant code: 77438230# (remember the "#"). Phone connection only upon request.

Items for followup from previous meeting

1. Testing of new cal modules to measure light output and determine the range of phoelectrons expected.
2. Sensitivity to Hadronic radiation: Stepan to provide information on damage to SiPMs during NH3 pol target run. (Stepan)
3. Detailed task list of everything that needs to be accomplished to flush out the use of SiPMs. (Elton, Fernando, Carl, Eugene...)
4. Input/Decisions needed to finalize Bcal readout requirements (See also GlueX-doc-1373).
   • Specify the normalization and dynamic range for the number of photons/GeV in showers
   • Decide on specific grouping for SiPM sums
   • Possibility of using air gap for SiPM coupling
   • Finalize shapes of "Winston guides"

Tentative Agenda

1. Announcements
2. Review of Action Items
3. Update - USM
   • First tests of SiPMs (Serguei)
4. SiPM - update
5. Light guides
6. Geometry
7. Discussion - MOU with USM

Minutes

Attending: Fernando, Lubomir, Tim, Pedro, John, Eugene, Beni, Elton (JLab); Zisis, George, Andrei (UofR); Will (USM)

1. Review of Action Items
   • Baby Bcal has been received at USM. Serguei believes that it has been in quarantine because it was shipped in a bare wooden crate.
   • USM should let us know how to treat shipping crates to avoid quarantine.
2. SiPM - update
   • George discussed tentative plans for testing 20% of SiPMs
   • SiPM shipment not yet arrived
   • Kathryn to transfer information regarding SiPM testing using samples
   • Laser head needs to be refurbished (about $5.5k) for careful measurements of SiPM PDEs. The laser is JLab's so fixes need to be funded by JLab.
   • There was a short discussion on the status of SensL: They will evaluate their options for delivering samples that satisfy all our requirements.
3. SiPM radiation hardness
   • Serguei sent the following reference regarding SiPM radiation hardness: P. Bohn et al., "Radiation damage studies of silicon photomultipliers," NIM A598 (2009) 722.
4. Light guides -tests
   • For reference: top = 2.525 cm, side =2.0 cm, bottom=2.4026 cm, cone to radius=1cm, Winston cone to radius=0.6cm (GlueX-doc-1077), efficiency=81%.
   • Preliminary results for collection efficiency for trapezoidal light guides (inner outside top geometry) with air gap:
   • Intput: top = 2.525 cm, side =2.0 cm, bottom=2.4026 cm, length = 8 cm
   • output: 1.2cm x 1.2 cm square
   • Ratio of input/output areas = 0.29
   • 1 mm lucite transition piece: efficiency = 87%.
   • 1 mm air gap, efficiency = 45%.
5. Light guides - discussion
   • The calculations should be checked but it appears that about 50% of light is lost at the air gap
   • Will suggested putting the air gap between the light guides and the calorimeter (instead of between the sensors and light guide). This suggestion was well received and generated considerable discussion. This option would allow an entire readout assembly including light-guides, sensors and electronics to be assembled on the bench before installation.
   • Pedro noted that any air gaps will collect dust and degrade transmission. The light-tight enclosure should be relatively clean.
   • Zisis: A spare "readout assembly" could be kept to trade out faulty assemblies during repair.
6. Discussion - MOU with USM
   • Will promised the updated MOU shortly, which JLab can use to circulate with the project management.