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Archived Messages for CLAS_DRIFT_CHAMBERS_1996@cebaf.gov: DC news and new plans

DC news and new plans

MAC MESTAYER (MESTAYER@CEBAF.GOV)
Tue, 19 Nov 1996 12:22:22 -0500 (EST)

Drift Compadres;
There are many tasks to do in commissioning the drift chambers; the list
is long. As for priorities, I listed items in the order in which I thought
they should be done (in May, '96). To help our thinking, let me re-write
the list of tasks as a list of goals instead.
--------------------------------------------------------------
FINISH INSTALLATION
1) Finish construction of the chambers incl. gas bags.
2) Do on-board instrumentation (daisy-chaining, installation of STB's,
HVTB's, de-humid. bagging) and on-board cabling.
3) Condition chambers - flow working gas, purge air, slowly turn up
high voltage as current decreases, keep boards dry, look at each sense
wires' signal on 'scope.
4) Install chambers, route and connect cables.
5) Install rack electronics, terminate and connect cables: same for HV
and lv supplies.
6) Install DAQ and trigger cables.
---------------------------------------------------------------------
VERIFY ELECTRICAL INTEGRITY of CHAMBERS
7) Measure continuity and isolation of wires to be sure there are no
broken wires and that chambers are electrically isolated from the outside
world (cryostat, etc.) except for grounding at HV distribution boxes.
---------------------------------------------------------------------
VERIFY ELECTRONICS and DAQ FUNCTIONALITY
8) Verify functionality of electronics system (from STB outwards to DAQ) using
pulsing.
---------------------------------------------------------------------
MEASURE ELECTRONIC NOISE LEVEL and SET DISCRIMINATOR THRESHOLD
9) With all cables plugged in (lv, HV, ground strap, signal) to their proper
places and with lv ON, observe noise level on amplitude section of ADB.
10) If noise is higher than the present threshold value (30 mV), increase
thresholds.
---------------------------------------------------------------------
VERIFY THAT GAS SYSTEM IS OPERATIONAL
11) Evaluate list of impurities from outside gas analysis.
12) Verify flow control; simulate a sudden leak by throwing open a valve;
simulate a crimped input or exhaust line - verify that safety responses work.
13) Verify that oxygen and water monitoring is on and calibrated.
---------------------------------------------------------------------
DETERMINE HIGH VOLTAGE OPERATING POINT
14) Do plateau using scintillator-gated scalers on ADB output; set all regions
to same gain.
---------------------------------------------------------------------
MONITOR CHAMBER PERFORMANCE ON-LINE
15) Look at monitor histograms (2d and 1d plots of hits vs. wire-number,
raw time and time difference histograms, and single-event display).
These do not require tracking.
16) Monitor high-voltage current draw.
---------------------------------------------------------------------
MONITOR TRACKING PERFORMANCE
17) Look at residual distributions (1d and 2d vs. DOCA, angle, etc.)
---------------------------------------------------------------------

So much for GRAND PLANS (GP); what about ACTUAL WORK (AW)?

AW for this week:
The electronics instrumentation is in full swing under the direction of
Peter Bonneau and Amrit Yegneswaran. High voltage distribution boxes
are in place and HV cables are being terminated and connected. ADB and
TDC crates will go in soon. George Jacobs is directing the cable routing
from cryostat to racks. Cryostats 4, 6, 8, and 10 o'clock have been
completed. 12 o'clock is progressing, 2 o'clock will be done after the
December run, after the 11 o'clock chamber is installed.
ADB board testing is well underway. Some problems have been identified;
most of which are due to occasional use of incorrect components. A few
ADB boards are being modified to provide a convenient point to monitor on
a 'scope the analog signals.
Steve Christo and Dan Carman are setting up a cosmic ray trigger. This
is not THE official cosmic ray trigger but should provide a convenient
trigger for the oscilloscope or for QVT's, scalers etc.
Hardware for monitoring individual chambers gas flows has been suggested
by Reinhard Schumacher and others. We will aim for completion before the
February run. Meanwhile, efforts will be made to determine gas leak rates
for the installed chambers "by hand".
Tracking software in the RECSIS framework is progressing well. BOS banks
have been established to provide track position information to the outer
detector analysis packages to match tracks with outer detector hits, and
also to pass back timing information to the tracking algorithm. BOS banks
have also been established to pass track orbit coordinates to the CLAS
single event display. The time and geometry calibration banks and procedures
are long since done. Jerry Gilfoyle is making progress on implementing a
calibration strategy for the drift velocity function. Sergei Boiarinov
is down-loading the electronics to wire map into the FASTBUS crate controllers.
Monitoring of raw hit and time information has been implemented within
the MONITOR framework (the online process devoted to monitoring detector
performance) by Elliott Wolin based upon early work done by Burin Asavapibhop.
Commissioning shifts have started. We started a logbook and are currently
helping with instrumentation issues (i.e. making cables) as well as neatening
and labelling gas lines and establishing grounding lines. We will begin
electronic noise studies and pulsing late this week or early next week.

Thanks to everyone for their efforts and especially their flexible attitudes
during this chaotic period.

"Chaos is good news." - Buddhist saying

- Mac