Subject: Decommission of MACRO's WFDs
From: Erik Katsavounidis (Erik.Katsavounidis@lngs.infn.it)
Date: Fri Apr 21 2000 - 18:39:23 EDT
MACRO colleagues,
As you know in less than two weeks we'll be unplugging the WFD system
from MACRO's acquisition. This raises a few issues that I'd like to
bring to your attention:
o RUN duration following May 1st
o Special trigger (monopole) and WFD calibrations before the WFD hardware
takes the airplane to Japan (~ May 10th)
If you have no interest in any of the above there is no need to continue
reading this e-mail.
o RUN duration
============
As of now, 80.5% of MACRO's data volume are WFDs.
Thus, by unplugging them, RUN duration will become ~5 times longer if we
were to keep the same file size of a MACRO RUN.
This is certainly impractical. The RUN size constant in the acquisition
system has to change. PHRASE can not handle runs longer than 12 hours.
After talking with Francesco, Aurelio and Max, the preference is to increase
the RUN duration to around 11 hours, i.e., twice the one today.
Originally I had a preference for keeping the RUN length (in hours) the
same as now; this is in order to remain compatible with various RUN
selection criteria adopted by the various analyses. However, Francesco
Ronga pointed out that having RUNs lasting longer will decrease the
number of files attached to every RUN, something that is quite convenient.
o Special Calibrations
====================
This is the last chance to perform any sort of calibrations that
require the WFD system. I think we should take all the time necessary
to perform a complete set of them. Here's a tentative list of them:
- Slow Monopole Trigger (TOHM/LI):
trigger efficiency vs. spe's for pulses lasting 0.5 to 6usec with
1usec step. In addition, pulses lasting 0.2-0.3usec (LI's nominal
threshold).
- FMT/Lamosska:
standard timing and amplitude LED calibration, enabling the WFD
readout; maybe some extra settings added.
- Laser:
We have never performed a systematic laser calibration of the
WFDs. Given the laser and WFD setup this is extremely tedious
and practically impossible. Before decommissioning the WFD system,
it could be a good opportunity to select representative counters
in the detector and map the high charge response of both the
WFDs and ERP using the laser. One counter per face can be a good
starting point.
We do not want these 'final' calibrations to become a never ending
thing. I suggest that we define the total time we'd like to spend
and try to accomplish as much as possible. If at the end of this
operation we find that we're missing crucial measurements, we can
re-examine our time deadline. Moreover, we should allow space for
a second iteration, i.e., perform the calibration once, analyze and
if the measurement needs refinement repeat once again. We all know
that we are dealing with fine tuning of devices that are intrinsically
hard to fine tune (LEDs, LASERs).
So, assuming that our friends from Pisa and our RUN coordinator
agree, I propose that we spend one day per uVax starting May 3rd
(Wednesday) and if deemed necessary we go through a second iteration
starting May 8th (Monday). During these final calibrations, the
rest of the detector (4 Supermodules) will continue taking normal
data on the main acquisition system (VXMACA).
Please let me know if you have any comments, suggestions or objections.
A presto,
--Erik
PS: we will keep a WFD crate (able to service a SM) fully operational
at GRan Sasso until the experiment's complete shutdown. THis will give
us the flexibility of performing in part of the apparatus any sort
of measurement that we have not anticipated.
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