User name R. Michaels
Log entry time 16:42:53 on July13,2003
Entry number 103791
keyword=L-arm Trigger Mods (part I)
This note pertains to modifications to the L-arm trigger and DAQ
prior to GDH July run. Since Robert Feuerbach did most work on
installing the new S2m detector, and knows more details about that,
I expect a follow-up halog from him.
Note, we did not touch R-arm setup since May running.
On L-arm there are now 4 triggers:
T1 = S1-or
T2 = (S1-or).AND.(Cherenkov-or)
T3 = (S1-or).AND.(S2m-or)
T4 = 2 out of 3 from among S1-or, S2m-or, and Cherenkov-or.
S1-or and S2m-or are the "OR" of the various paddles after first
requiring the 2 PMTs of one paddle both fired, i.e. a "paddle firing"
means the PMTs on both ends fired.
T3 and T4 are similar to May running. T1,T2 are new and should
not be confused with T1,T2 from R-arm. They exist in case something
goes wrong with S2m (e.g. a hole in efficiency).
If there is a physical overlap within 10 nsec at trigger supervisor, it
will show up in the datastream as event type 5. There are no trigger
T5. One should be able to tell which triggers co-existed by looking
at the trigger latch pattern (a TDC) as explained in online doc's.
However, we have arranged that T3 arrives well in advance of the
other triggers, so it makes event type 3. Under normal circumstance
one would set ps3 low and other ps factors high.
IMPORTANT: T1 has a lot of after-pulsing. The secondary pulses
come normally 460 nsec after the first, but also sometimes 1 - 3 micosec
after. No attempt is made to blank them off. I recommend running with
very large prescale factor ps1 to avoid erroneous deadtime calculation !!
The max ps1 is 2^24 - 1 = 16777215. We may even want to unplug T1
after we are confident S2m works, to avoid wrong deadtime.
In scalers, page 6 of L-arm xscaler display is the non-helicity gated scaler and
has T1-T4 from L-arm. The T1,T2 from R-arm was moved to channels
17 and 18. xscaler was re-labelled and a sign posted. Meanwhile page 9
of R-arm xscaler shows T1,T2 from R-arm. Simplest rule: Look for your
trigger rates on the xscaler display corresponding to that spectrometer.
24 of the 32 channels of S2m were plugged into available scaler channels.
Obviously we'll need to install more scalers before the next experiment.
DAQ: The configs are
LeftUnbuff -- Default config involving all crates. There is a new crate roc4
which contains an ADC and TDC for S2m.
pedrunL -- The usual pedestal run config.
LeftRoc311 -- A "minimal" config that involves only roc3 (fastbus) and
roc11 (scalers). This avoids roc4 and roc14.
At the moment I notice 9th and 10th Cherenkov channels are off on L-arm.
Perhaps someone is working there ?