Present at Gran Sasso:
Ioannis Katsavounidis, Massimo Orsini, Nicola Zaccheo (until Aug 6),
Valeriano Marrelli (until Aug 6), Sophia Kyriazopoulou, Chris Orth,
Charlie Peck
In general, MACRO ran very well during this period, although there was
the usual complement of relatively small difficulties. These and their
status are listed below.
1) For some time prior to Aug 5, there had been a problem with the SM6
top SMT, mainly "fake events", i.e., triggers with no information about
themselves in the indicative registers. Finally, the problem developed
into "No-Q" reports in addition and it appeared at a sufficiently high
frequence to crash the data acquisition system.
On Thursday morning, Aug 5, Sophia and Massimo laid the patient on the
operating table and executed major surgery. The patient's ACTEL brain
was carefully removed and it was found that the ligatures between its
nerves and the outside world needed serious resoldering. This
was done, gently and with feeling, the ACTEL was replaced, and the
patient replugged into her normal CAMAC slot. She now regularly reports
that she is feeling much better (but see later) and we can all tell that
she is doing her job happily and reliably. Cheers to Sophia and Massimo
for their skillful and successful intervention!
It should be added that those who have watched the history of MACRO for
long times know that problems of No-Q's started with the top SM 6 SMT
about a year ago. They then went away, and no efforts were made to find
and repair the problem. The moral of the story is that No-Q's should
not be ignored - they mean that something is wrong.
2) On or about July 30, the INTERERP TDC circuits began to produce large
numbers of No-Q's. Chris investigated and succeeded, by disturbing
cables, in makeing the No-Q problem go away, but then the INTERERP
monitors reported an excessive number of intererp TDC overflows.
Suspecting a broken TDC, Ioannis fixed a malfunctioning spare, but
replacing the suspect one with it did not solve the problem. However,
we now have an operating spare INTERERP TDC module. It was then
discovered that the cable carrying the CLEAR signal from the INTERERP
circuit to the TDC for microvax 1 was broken. It was fixed, and all of
the INTERERP problems vanished. It was realized, however, that the lack
of a CLEAR signal did not explain all of the problems observed earlier,
and in fact the next day or so, the excessive INTERERP overflow problem
reappeared. Ioannis prepared special analysis software to pinpoint the
problem and it was found that it could be explained by the lack of a
pretrigger signal from SM2 to the INTERERP logic circuit. By the time
this was discovered, the problem had disappeared. Conclusion: some
cable or connection on a module related to that signal is making a poor
connection. In spite of extensive exercising of the signal cables
related to this signal on Aug 11, the problem could not be recreated.
However, it is likely to arise again sometime in the future.
3) On Aug 6, monopole trigger calibrations for SM1, SM2 and N were
performed with 1 microsec and 0.2 microsec pulse widths. The 1 microsec
data appears to be satisfactory, but the shorter pulse data needs to be
retaken after modifications to the calibration control parameters. On
Aug 12, SMT trigger calibrations were done on SM3 and SM4 with pulse
widths of 1 microsec and 0.35 microsec. Again, the 1 microsec data
looks fine and the shorter pulse data requires more study and possibly
parameter adjustment.
Chris performed a normal laser calibration and in addition collected
WFDs from laser pulses from 1B08.
4) As often happens, a power supply on a PHRASE crate blew one of its
hot output transistors. The supply was replaced and we noted that the 6
volt line was supplying 80 amps rather than the usual 70. Massimo
turned off the crate, pulled all the modules, then reseated them. The
supply now is supplying its normal 70 amps. All looks well now, but it
seems that the mean time between failures of these output transistors is
a few months. Are there better transistors (i.e., higher power rating)
on the market now, ten or more years after the PHRASE system was
initially built?
5) It can be unambiguously stated that there was a partial solar eclipse
in L'Aquila on Aug 11, culminating in about 80% obscuration at
12:45pm. Ioannis and Chris are to be commended for building a very nice
pinhole camera with which we could all clearly see the effect with no
worry that our eyesight might be damaged. MACRO's counting rate was not
noticibly affected by the astronomy, and we
believe that, expectations notwithstanding, fewer than one monopole was
observed during the event, although Sophia has not yet finished her
analysis of the Aug 11, 1999, data.
6) LATE ADDITION: Sophia reports that the SMT from SM6 top is again
showing multiple fake events! Perhaps more resoldering is needed?
A presto!