Notes on Trigger Programming for e99117 and Beyond
==================================================
update May 20, 2001, R. Michaels and B. Reitz
Software and notes in adaql1:~atrig/trigger/mlu
Note: some stuff stored in ./save20may01, e.g. old MLU
files no longer used. See also README* for earlier
experiments.
I. Overview
The main spectrometer triggers T1 (R-arm) and T3 (L-arm)
are formed from an overlap of S1 and S2 scintllators.
Note, these main triggers do not involve an MLU any more.
The triggers are
T1 = Main R-arm trigger
T2 = Loose R-arm trigger, for measuring efficiency
T3 = Main L-arm trigger
T4 = Loose L-arm trigger, for measuring efficiency
T5 = coincidence of T1 and T3.
The MLU is used to form T2 and T4. It can also be used to
form additional triggers that require other detectors.
Let us first describe the MAIN TRIGGER, T1 and T3, which
is based on scintillators. First the Left and Right PMTs
are AND'd. There are then 6 signals from each scintillator
planes S1 and S2 (the result of L+R). These 6 are OR'd to
make one signal each from S1 and S2. Finally, the trigger
is the AND of these two signals. Here is an ASCII diagram:
S1 - paddle 1 - Left --\
S1 - paddle 1 - Right ---AND -->
S1 - paddle 2 - Left --\ \
S1 - paddle 2 - Right ---AND --> \ OR of S1
paddle 3... 6 \
\
\ AND -------> T1 (T3)
/
/
S2 - paddle 1 - Left --\ / OR of S2
S2 - paddle 1 - Right ---AND -->
paddle 2... 6
Trigger T5 will be formed as a coincidence between Left and
Right spectrometers. Of course, this is irrelevant for single
arm experiments like e99117, but we will try to make it ready
anyway.
The timing at the trigger supervisor will be such that T5 arrives
first and takes priority in deciding the event type. However,
one may look at the trigger latch pattern to see which triggers
coexist.
A ``trigger latch pattern'' in the datastream shows the
pattern of triggers which co-exist in an event. This is
a TDC 1877 (multi-hit with up to 6 hits, a 5 microsec
window, one trigger on each of 12 channels, each channel
a separate trigger) which shows on channels 1-12 the
trigger 1-12 AFTER prescaling. So, if a T5 is accompanied
by a T3 which survived prescaling, one would see a signal
on channels 3 & 5 with the appropriate timing. This
trigger latch pattern is called ``spare7'' in the detector
map.
II. MLU Programming -- Concepts
Since Jan 1, the S-Ray trigger plays no role anymore.
Notes on this exist, but not here.
MLU for T2, T4 -- Identical for Left and Right Spectrometers
Greatly simplified compared to the past, this MLU now
runs in strobe mode. The strobe comes from "OR" of
S2-R and S1-R (i.e. Right PMTs of S2 and S1) where S2
is timed to arrive first; hence normally S2 makes the
timing but if it is absent due to inefficiency or whatever
then S1 makes the timing.
Inputs
1 = S1-or
2 = S2-or
3 = Gas Cerenkov -or
Logic
Put out bit 1 (and bit 3 is a copy) if S1.and.S2 exists.
This should be identical to the main trigger, however
the main trigger is formed by a separate logic unit and
is therefore immune to MLU deadtimes. We will scale the
output of bit 1.
Definition of T2 (same for T4): Exclusive of the above logic,
we put out a bit 2 (and bit 4 is a copy) if one of the following
conditions exist.
Cerenkov and S1-or (but not S2-or)
Cerenkov and S2-or (but not S1-or)
Generate T2, T4 with
mlu_t2t4_generate.dat
III. Technical Details of MLU Programming
The following script generated the MLU file for a1ng2n (e99117, etc)
======
#!/bin/bash
# Generate the MLU file used to make T2(T4) for A1n/g2n
#
XYmlu -f mlu_t2t4_generate.dat
# (output is 'mlu.data')
#
mlu_compress mlu.data
# (output is 'mlu_compress.out')
#
mv mlu_compress.out mlu_t2t4.data
=======================================================
Appendix -- MLU utilities routines
(Ported to Linux, Jan 2001)
Type the name of the utility without arguments and
it will introduce itself, and explain its usage.
XYmlu -- takes a pattern like 10xx01 and
generates all mlu entries. 1=bit must be true;
0=bit must be false; x=bit may be 0 or 1.
There is a Y option, but it is little used
and not too important.
btst -- Examines a pattern of bits
mlu_compress -- Takes an mlu file and
examines all pairs of line-entries. If the
two line entries are identical, one is kept,
the other discarded (this isn't really necessary
but speeds up the download). Also the bit-wise
OR of 2nd components is taken if first components
are identical.
mlu_compare -- Compares two mlu files
to see what is different. If no optional
argument is given, any difference in the
file are noted. If an argument is given
(any number), only the first entry of each
pair are compared.
mlu_bitmerge -- Merges two mlu files. For
each pair of line entries "X1 Y1" from file 1
and "X2 Y2" from file2, if X1=X2, then the
two entries are merged to form bit-wise OR
of Y1,Y2, i.e. we get "X3 Y3" where Y3 = Y1 | Y2.
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