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User name Bob / Julie
Log entry time 10:33:14 on November11,2010
Entry number 339536
keyword=helicity issues, part NWork done by Bob Michaels and Julie Roche
Regarding the helicity problems in scaler, ring-buff, etc.
We went to the Left HRS and checked all the helicity signals on
a scope, one more time. They look clean (no mult. pulsing) and
the timing was ok.
Recall that last Friday I (Bob) made some repairs (see halog). After
run 8384 the data were cleaner (fig 1) but there is still a tail of
runs with large lost times (600 sec max out of a normal 3600 sec
run). There is also a slope of the lost time versus time of run
(fig 2) but I think this is artificial. This slope can be made zero
by fine-tuning the gate-off time at the level of 0.5% which we have
not done yet. So the only problem is the tail to large lost time.
The one improvement we made today was to increase the width of the
signal for the LNE. Previously it was 35 usec but now it is 970 usec
which means that if Qweak decides to flip at a rate above 1 kHz we'll
lose scaler data. I guess it's doubtful they will do that. The
large width will help kill double-pulsing.
As far as what to do about the problem, I propose to leave the
electronics alone. Its failure rate is small and we don't really
know which module is failing though I suspect one fanout (and I
don't know where a spare is). For the analysis, I suppose we'll
need to use a combination of the ring buffer, TIR, and clock to
make a robust recovery. It hasn't been tried yet.
FIGURE 1
FIGURE 2
