AT start of shift efficiency was 71%
(in the end it gets better)
First I noticed that there were pages TORN out of the logbook!
Why was this done?
This is poor lab practice as they may have contained valuable
information. If it is wrong just put a line through it.
RUN 1648
Added 11nsec (91" cable) delay to TDC start cable
Efficiency = 75% (so this was a 5% improvement)
RUN 1649 (double check same setup w/higher stat)
Eff=75%
RUN 1650 Delayed CS ~6nsec (mid-run) left 11nsec delay in place
verifying changes on scope
See prior Blast_ToF emails
Eff=36%
RUN 1651 garbage
RUN 1652 removed CS delay, added 91 more inches to TDC start
(as this helped earlier)
Eff=0% as no events were seen by the bottom tube
(clearly the wrong thing to do)
RUN 1653 removed ~45" of TDC start delay
Eff=70%
RUN 1654 removed ~45" delay (back to 91" delay)
and ran T1 thru delay box with all switches unset
verifying changes on scope
Eff=73%
RUN 1655 set 8nsec delay switch on T1 delay
Eff=0%
CS had been oscillating between ~10nsec before and 10nsec after T1
switched RETIMING OR output from pin(s) 4 to pin(s) 8
Then ran CS back into delay box with switches unset.
This caused CS to oscillate between 2 and 12 nsec AFTER T1
This above move proved futile as efficiency dropped to near zero.
Moved retimingOR back to pin(s) 4 and checked TDC stops against backplane
common start again. LTOFTOP1 arrives about 50-75nsec (fluctuating) after
start, LTOFBOT1 arrives in just under 60nsec and does not fluctuate as
much as the TOP. (also both raw tube signals looked similar)
RUN 1663
Added ~20 nsec delay with extra cables to LTOFBOT TDC stop so
it is only 5nsec or so after TOP.
Eff=76% So it seems TDC timing diff is not the problem.
RUN 1664 removed the common start 91" delay
Again eff=76% so the "improvement" earlier must
have been an error.
OK here is where it gets better...
RUN 1667 lowered LTOF1BOT threshold from 41mV to 20.9mV
Eff = 94% (that helped)
We had 99% efficiency with a 41mV threshold earlier
so I did not drop the threshold until late in the shift.
Besides the raw tube signals looked identical on the scope.
RUN 1669 set both LTOF1BOT and LTOF1TOP thresh to 20.9mV
(small paddles are at 20.9mV)
Eff = 95%
RUN 1670 at LTOF0 by taking dominating LTOF1 trigger conditions
out of trigger (all prior efficiencies were for LTOF1). Set all
thresholds to 20.9mV
Only saw 30% efficiency for this one.
But the raw TDC spectra for this most forward small paddle has two
large spikes as opposed to the TOF tubes. Is this a very noisy small
paddle?
RUN 1674 reloaded TOFefficiency.settings
so that LTOF1 is back.
Eff for LTOF1 = 98% (with 18000 events)
So it's still good!
I recommended that Tavi take a look at LTOF0
since things look pretty good for LTOF1.
Pete
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