CountingDaq 210303

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Meeting information

 Meeting time:  3:00pm Eastern
   
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Agenda

• Desired trigger configurations trigger
• Discussion of preliminary design review
  • Cabling and crate layouts
  • FPGA trigger concepts
  • Event data structure
  • Data and event rate estimation
  • What are the requirements and the interfaces to other subsystems
  • Grounding and shielding
  • What are our requirements for deadtime, trigger rate, etc
  • What else do we need to define?
• General discussion
  • No meeting on March 17 due to review on the 18th, so next meeting will be March 31

Minutes

Participants: B. Moffit, C. Ghosh, D. Armstrong, H. Liu, R. Michaels, P. King

• Desired trigger conditions
  • Scanner #2 detectors are the three linear scanners; these are probably always left in integrating mode. David indicates that their main use is with the magnet off to find the collimator edge
  • The standard trigger will likely be just the trigger scintillators in the 7 septants: AND the two PMTs in each sector, then OR of the seven septants.
  • For more complex triggers, especially for coincidences between thin quartz and the other channels, we would need to form coincidences between the two VTP modules
    • With removing the discriminators and VETROCs, one VXS crate could hold all of the thin quartz channels (14 FADC), and a second VXS crate would hold the remaining seven FADC.
    • In the current design, the VTP modules would communicate with a TI-master in one of the two VXS crates. The TI has six trigger inputs, so it could handle forming coincidences between three identified trigger combinations from each of the two VTP modules.
    • Following the meeting, Hanjie forwarded a comment from B. Raydo that indicated that the VTPs can share 32 channels of FADC trigger data over on of the four optical outputs. This is used in the CLAS12 ECAL trigger and HPS. This information can be more processed by the VTP than just the FADC hits; for instance HPS shared clusters.
    • We should try a test of the sorts of coincidence triggers we might want to do using two VTP modules, to verify we would be able to form those sorts of triggers
  • Bob asks if we would actually want to form the trigger in NIM modules. I would prefer to not do that, but to use the VTP to have the flexibility of defining the trigger conditions. Also, to form a trigger in NIM with the option of including all the thin quartz, we'd also need the splitters and discriminators and many more NIM modules that we have planned so far. So the VTPs are likely both more flexible and lower cost.
• Further discussion of the trigger
  • We will need to get some experience in how to set up the VTP triggering.
  • How will we adjust the relative timing of the VTP trigger? What kind of timing window do we think we need?
    • David expects that the trigger scintillators probably have some few ns of jitter/slewing we'd need to be able to handle.
  • When do we need to have a test-stand that demonstrates the sort of VTP triggering modes? Probably by the end of this calendar year, so that we know we can move ahead with full procurement in 2022.
• Discussion of cabling crate layouts
  • The MPDs need to be close to the GEMS. Their inputs are HDMI cables and should be less than 15m long. The output connections to the SSPs are fiber connectors, so the length can be long.
  • The "close bunker" would have 2 VME crates for the MPDs, and 2 NIM crates for the amplifiers. What else goes in there?
• Design review on the 18th
  • David asks when the counting mode discussion will likely occur, as he would like to be in the meeting for it and has other obligations. I estimate that it would likely be 2:30-3, and he'd be available then.