Minutes 060609

Notes for item 2, tagger and trigger timing, etc (from EJW):

1.  We should install He bags;  need to submit requirements doc to H-B for this and other beamline components
    incl. radiator thickness, collimator size, pair-spec and other magnet needs, etc.

2.  Tagger trigger timing (thanks to Eugene Pasyuk):
  20 ns      transit time in T-counter PMT
  50 ns      cable to CFD
  10-15 ns   internal CFD
  5 ns       cable to L-R coincidence module
  5 ns       internal coincidence module
  10 ns      cable to Master OR module
  20 ns      internal Master OR
  80 ns      cable to forward carriage
  50 ns      patch cables from forward carriage to BCAL test trigger rack
  -----
  250 ns     signal delay electron hits radiator until Master-OR arrives at our rack

Note that photon flight time to alcove is approx 100 ns (check with Mike Zarecky).  Also note that T-counter
cables are trimmed to give equal time signal at L-R coincidence module.

If I recall,  Richard said RadPhi has both 250 ns cables and 80 ns cables running from the 
alcove to the RadPhi racks.
  
Still to be determined:  BCAL signal timing, time to create BCAL trigger, length of cable running from
forward carriage back to tagger, etc. 

3.  Tagger uses LeCroy 1877 multi-hit and CAEN pipelined TDC's; both run in common-stop mode.

4.  CAEN V792 ADC (BCAL readout) is slowest and sets front-end busy time.  May skip busy and just 
    use front-end-busy-timer in TS, as V792 has fixed digitization time of approx 7 microsec.