OWG meeting 29-Aug-2007

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Overview

This is a special one-topic meeting whose goal is to try to understand the event size given the recent simulation results on occupancies, especially in the FDC. Note that the 2002 Hall D design document lists a 4kB average event size, although it is possible that the FDC itself may take 4kB (or even more). The average event size affects the design of the DAQ system in a number of ways, so this needs to be understood sooner rather than later. Fortunately the DAQ architecture is highly scalable, so accomodating higher event sizes and event rates is not a big problem.

The goal of this meeting is to:

  1. Understand what we know and do not know about event size, occupancies, etc.
  2. Devise a plan to learn what we need to learn


Agenda


Time/Location

1:00pm Wed 29-Aug-2007 Cebaf Center F224

To phone in, send me your telephone number and I'll call you.


Announcements

Next Meeting

  • TBD (some of us will be out of town the first week of Sep, and OECM review is second week of Sep)


New Action Items from this Meeting

Minutes

In attendance: Simon T, Fernando B, Dave A, Elke A, Eugene C, Elton S, David L, Graham H, Elliott W, Gerard V (by phone).


Fernando gave an overview of the latest electronics channel counts, some of which need to checked by the detector experts. Maximum card counts are 18 for VME64X and 16 for VXS. He noted that the channel count table is not optimized yet for detector locations, cable routing, etc.

David L presented the latest Monte Carlo results on event size. These studies are still in progress. Results presented were from work done by Dave, Matt (from this past spring, based on 100M gammas), and others. Some results were based on older FDC designs, and must be redone with the latest geometry. Some results included only electromagnetic processes, and not photon-induced hadronic processes. Some notes from his presentation:

  • FDC cathode rates are higher than anode rates
  • 8 MHz worst case per FDC plane
  • 4-5 FDC cathode hits per anode hit using fixed thresholds
  • main contribution to TOF backgrouns was from the 2 micron copper strips in the FDC
  • CDC results were from both MC and from calculation
  • for 9 GeV photons the average number of hits per event per detector (we need worst case, too) are: 452 FDC cathodes, 54 FDC anodes, 70 CDC, 4 SC, 100 BCAL, 12 FCAL, 14 TOF, giving approx. 700 hits per hadronic event