Present at Gran Sasso: Lori Gray, Erik Katsavounides, Ioannis Katsavounides,
Sophia Kyriazopoulou, Paolo Saggese, KS, Stefano Stalio
WEEK 1: November 4, 1996
-- Welcome to Ioannis Katsavounides (hope I got the spelling right)
who will be working as a US tech, with both hardware and software
responsibilities. He's been spending his first weeks soaking up MACRO
lore.
-- Sophia reported on the fire in the galleria auto (she will write up
a description in her shift report.) Things seem to be more or less
back to normal now, with no apparent serious damage to any electronics
from the power disturbances associated with the fire, although
currently there seems to be a slightly higher rate of minor problems
like ST planes tripping off and power supply troubles.
-- TOHM/LI: The last few broken channels of the new attico TOHM/LI
need to be fixed. Sophia and the techs will try to finish off this
job before the collaboration meeting. Paolo has built a test box to
help with automated testing of replacement boards from Caltech. He
had some power problems with it, which will be fixed shortly.
New TOHM/LI clock distribution boards have chips in them which
overheat and tend to last only a few months. To fix the problem Paolo has
ordered thermal glue and heat sinks. The thermal glue is here, but the
heat sinks, which were supposed to arrive months ago, haven't yet
shown up. He'll try to track this down. Sophia is going to redo the
board when she gets back to Caltech. She must start from scratch
because the lost the files; however it is a simple board.
Stefano has been working on fixing up the last few disconnected/broken
channels of the lower detector old TOHM/LI. These fall into a couple
of classes. Some result from hot pmts; however nothing is obviously
wrong with the spe signals of these tubes viewed on an analog scope.
These are actually tubes with a high rate of afterpulsing
(afterpulses following pulses even as small as ~100 mV with a ~1.2
usec delay, indicating the presence of helium in the tubes. There
were many such tubes in the west face -- perhaps pointing to ST
leaks?) Stefano has been replacing the afterpulsing tubes. The other
class of old TOHM/LI problems involves bad electronics; the techs have
been fixing and replacing various channels. They noted one TOHM board
which gave double TOHM pulse outputs; this was tracked down to some
traces which should have been cut but weren't. A systematic search
for this problem was suggested.
-- The good LeCroy scope, which apparently enjoys touring abroad,
still has a bad channel, even though it was recently sent out to be
"repaired". Paolo will investigate sending back the scope yet again,
or perhaps getting a new one.
-- WFD: The techs fixed some oscillating waveform channels by
removing capacitors. Ed Kearns' WFD monitoring software can
point out problems like this.
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WEEK 2: November 11, 1996
-- Paolo has been working on his nifty offline histogram presenter
which uses data from Erik's monitor jobs. He's been adding small
improvements.
-- All power supply casualties from the disturbances caused by the
fire (2-3 of them) have now been fixed by the techs. The 4 PHRASE
supplies that died have also been dealt with.
-- The SM 1 FMT has been giving high rates, and the cause is still
unknown. It was suggested that the fan-in module should be replaced.
-- The TOHM test setup, which had had some power supply problems, was
fixed by Paolo. He and Ioannis have started testing TOHM cards with
it.
-- Stefano has continued to debug lower SMT problems, with Ioannis.
They replaced some lower TOHMs but are not sure of the accuracy of the
threshold setting. They have been investigating whether the stability
of the power supplies can affect the stability of the thresholds.
-- Ioannis and Stefano have also discovered that the old BU fanout
module used for distributing LED signals can be unstable in its output
over timescales of the order of ~30 minutes. This can be a serious
problem for doing monopole calibrations. They have also discovered
some strange features of the old BU fanout output: it can give strange
spikes on the leading edge of a square waveform. This can affect
monopole calibrations by causing the LED to fire early for driving
pulses that without the spike would be too small to fire the LED.
More investigations are in progress.
-- WFD: Ioannis was able to fix another oscillating WFD channel
by removing theusual capacitor culprits; however another problem
module was found to have already had its capacitors removed. It's
not clear what to do about this channel.
-- WFD overshoot: Doug has been investigating a problem which may
cause loss of sensitivity for monopoles. It turns out that the pmt
fanouts are AC-coupled at the output, so that large pulses are
followed by an exponentially decaying positive overshoot. The problem
is that the WFD records the positive information over a 2.5 mV
threshold. For big enough pulses the overshoot goes on long enough
that the WFD buffer fills up -- and since it reads out backwards in
time the actual big pulse that caused the overshoot can get lost.
Doug has checked this explicitly by injecting pulses into a fanout and
verifying that the overshoot behavior is consistent with an RC
circuit. He has calculated the expected overshoot for monopole-sized
pulse charges, and has determined that our sensitivity is limited for
betas much higher than about 10^-3. So this is really a high priority
problem that we should address immediately.
Doug has compiled a list of suggestions for fixing this problem, all of
which have their relative pros and cons. The simplest solution is simply
to turn off the waveform recording for positive pulses (although this
will decrease our ability to reject bipolar noise); more complicated
solutions involve hardware fixes to the waveforms or the fanouts.
This issue will be discussed extensively at the collaboration meeting.
-- LUTS: The regular ERP LUT-iteration procedure has not been
performed since Maurizio left; I have fired up the software again so
that the ERP LUTS (GC and muon) can be reset for smooth running when
the PMT gains start to get reset next week. Last summer Rich pointed
out that some (maybe ~1/4) of the vertical tanks have wacko LUTS with
fewer GC than muon bits set on one side of the tank. I tracked this
down to a bug in LUTGEN, the LUT generating program (not the LUT
iteration algorithm). This bug is now fixed. In view of the fact that
some of the LUTS are wacky, the new iterations will start with fresh
LUTs based on the most recent calibration constants.
Before, part of the LUT iteration procedure ran on VXMACB and part of
it ran on rsgs02 (for various historical reasons). This setup was
awkward, and in addition rsgs02 is not as reliably maintained as
VAXGS; also VXMACB's CPU is overloaded and it is preferable not to
overload with interactive processes so as not to decrease the ERP GC
monitor efficiency. For these reasons I set up the whole LUT
procedure on VAXGS. The raw data must now be copied to one of the
VAXGS scratch disks; the procedure is now slower, but not cripplingly
so.
-- Nat has brought the monitoring boards designed/built at Swarthmore
and Boston with him. These are designed to perform a function similar
to a DSP module, e.g. crate voltage monitoring, for both VME and NIM.
Some are VME boards for the waveform crates -- they are now stuffed
and ready to plug in. Nat's NIM crate monitor boards
are not yet stuffed. The techs will perform the stuffing and
installation over the next few weeks.
-- Next week, as I mentioned, PMT gain resetting will begin. The
last gain resetting was a year ago. In addition, some tankend
maintenance will be performed. EMI tubes only will have their
gains reset; the Ham signals still look pretty good.
That's all...
Your humble shiftworker,
Kate.