Happy Holidays. We just completed the December run, and we learned a lot.
The mini-toroid works pretty much as expected in shielding the inner
chambers from target-related background. Drift chamber DAQ was never
operating properly but the chambers did NOT draw excessive current in beam-on
conditions.
We identifed three critical problem areas:
1) Some connectors were not plugged in properly in the Region 2 chambers.
They were probably loosened by the cable strain relief. The ODU team
is checking out each of the signal and low voltage connections. Any
faulty connections will be corrected before the relevant Region 3 chamber
is installed.
2) Noise levels in the hall were higher than expected. Noise levels were
approximately proportional to wire length. Last night we conducted a
search for specific sources of the noise. I'm happy to say that we
found the culprits: 2 LeCroy high voltage crates used for the Tagger
photo-multipliers and 1 VME crate on Level 1 North. For the wire which
we selected (Reg. 3, Sec. 5, cable 16.3, chan. 1) the noise consisted of
bursts with a definite time signature with a peak amplitude of +- 65 mV.
After turning off the three crates mentioned, the noise level was
about +- 7 mV with no discernible features.
3) Drift chamber DAQ was not operating properly. A team of Dave Tedeschi,
Brian Quinn, and Burin Asavapibhop are working with technician Michelle
Briesel (one of the Reg. 3 stringers) to develop a test setup in the
EEL building with an ADB crate, a FASTBUS TDC crate, a pulser and a
DAQ computer running CODA. Does anyone else in the DC group wish to
participate in DAQ issues?
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Now to other progress.
First, thanks to Larry Weinstein for his to-do list.
CONSTRUCTION:
- R1 construction and instrumentation:
Last night (12/17/96) the 6th and final Region 1 chamber was delivered
to CEBAF; driven here by Gary Wilkin. Congratulations!
- R2 checkout:
All six chambers are being checked for proper connection of the
signal and low voltage cables. George Jacobs is leading the effort
to locate and seal gas leaks in the chamber.
- R3 construction and instrumentation:
Two R3 chambers have been installed: at 5 and 7 o'clock. Early next
week we will install the 11 o'clock chamber.
- Drift chamber cabling:
Great progress has been made on drift chamber cabling thanks to the
efforts of many people led by Amrit Yegneswaran and George Jacobs.
All cables have been installed and routed except those going on the
2 o'clock cryostat.
- Gas system:
Cleaning of the buffer tanks is proceeding, to be followed by a
checkout of the entire system in January.
- ADB boards:
ADB testing has been streamlined. Approximately half of the boards
have been tested and accepted.
- Pulse calibration system:
More progress has been made on the pulse calibration system. We can
now remotely pulse the trigger calibration interface (TCI) boards
and the trigger supervisor. Once DAQ problems have been resolved we
will work toward installing a file-driven system.
Tracking within a RECSIS framework:
Hit-based tracking is ready to go on real data. Work is ongoing to
allow RECSIS to run from the DD ring.
Other progress?:
Post it to CLAS_DRIFT_CHAMBERS@CEBAF.GOV !