Oct 7, 2010 Readout

Teleconference Time: 11:00 a.m. EST

• ESNET and EVO session
• Phone in CC L207 is 757-269-7084
• 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. Collect this information of testing (including goals and setup) on the wiki for ease of presenting information. (USM)

Tentative Agenda

1. Announcements
2. Review of Action Items
3. Update - USM
4. SiPM Radiation Hardness Test (Update from Yi)
5. Electronics/cooling
6. Geometry and light guides
7. Simulation runs

Minutes

Attendees: Eugene, Fernando, Beni, Yi, John (Jlab), Zisis (Regina)

1. Announcements: none
2. Review of Action Items: A new item has been added, concerning a NIM article on SiPM radiation hardness.
3. Update - USM: no report.
4. SiPM Radiation Hardness Test (Update from Yi)
   1. The decision to proceed with SiPMs was taken in yesterday's Hall-D meeting. Glen Young has been informed, but the decision has yet not been communicated higher up. We have used up one month of our float and need to proceed to procurement soon.
   2. Sasha found a paper that showed measurements of afterpulsing down to 100 K, of the order of a few percent. Neither Carl nor Yi have seen anything noticeable, but Yi will closely examine the pulse shape at room temperature and also at 0 C. Hamamatsu puts a strict range on Vop, in order to minimize this effect.
5. Electronics/cooling:
   1. As soon as the SiPM decision is official, Fernando will get the BCAL CAD file from Chuck, import it into the electronics CAD system and start working on dimensional details for electronics and cooling.
6. Geometry and light guides:
   1. Tower summing: The summing of SiPMs into towers may have a negative effect for the inner most layers. Perhaps the SiPMs summed into the inner tower can be read out individually; this would require 400 additional electronics channels at a cost of $200k. It would also have a minor impact on the electronics density. The dynamic range is a weak justification towards using towers -- cost was the major driver. It is not clear how the summing affects the resolution and thresholds for different incident particle energies and angles. Simulations are needed before a final decision is taken.
   2. $500k has been assigned for development of the electronics and cooling for the SiPMs, including temperature stabilization and mechanical. The amount must be spent in a three month period. Manpower must be sought to carry out this work and take advantage of the funds.
   3. Light guides: This is a topic that has moved up in priority this fall. There are many issues to be resolved.
      • Athens has conducted measurements comparing the Winston Cones (Wicos) versus the Chile truncated, trapezoidal light guides (Traps), mounted on a baby cal with optical grease. No difference in efficiency was observed, contrary to what is expected. The Traps offer mechanical advantages in mounting any monitoring system, including a square exit that better matches the SiPM active area.
      • Eugene brought up the issue of temperature variation and gradients near the LGs, which may point to using a fibre to bring the light from the LED to the LG, while using fewer LEDs and thus simplifying the "monitoring of the monitors" (Beni).
      • The current plan is to glue the LGs to the calorimeter and leave an air gap on the SiPM end, although a Si cooker or RGB glue should be considered as well. Wicos have a larger exit angle that would benefit from this.
      • Highly reflective wrapping (a la TOF/FSU) should be considered, although this might deteriorate timing.
      • TRIUMF used a CNC machine to make the Wicos. Regina will get prices and time schedules from the TRIUMF scintillator shop.
      • Zisis will guide this effort and has set up a Wiki page on Monitoring R&D.
7. Simulation runs: no report.