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Archived Messages for HALLA_MIN_1997@cebaf.gov: Minutes
Minutes
John LeRose (lerose@CEBAF.GOV)
Thu, 10 Jul 1997 14:35:32 -0400
Minutes of Hall A Group Meeting 8 July 1997
1 Beam Reports: Three test plans run last week, Møller
Polarimeter, Lead Glass, and Parity prototype
detector.
1.1 Møller Polarimeter: ( A. “Sasha” Glamazdin
reporting)
1.1.1 1st tests completed
1.1.2 In general things look reasonable.
1.1.3 Some problems with detector positioning.
Will adjust.
1.1.4 Target effectively cooled to 180 K
1.1.5 Observed differences in measured
polarization of the beam depending on the
polarization of the target. Not
understood, they’re working on it.
1.1.6 Polarized beam was good (30 microamps with
long lifetime)
1.1.7 Question re shift report for the last 4
hours of beam time. It was already taken
care of.
1.2 Lead Glass tests: (Bogdan Wojtsekhowski)
1.2.1 Explained setup: Lead Glass array 5 m from
target in coincidence with the Hadron Arm.
1.2.2 Showed summary of observed count rates vs.
threshold and with and without water
flowing through the target. In general
things were quieter than expected.
1.2.3 Coincidence timing spectrum looks very
clean.
1.2.4 Results in general very good and
encouraging. Planning to upgrade to a
better detector in the fall.
2 Hall Status:
2.1 Ed Folts reports:
2.1.1 Had a fire drill today and we failed
because someone walked into the Hall in
the middle of it in spite of the alarm.
General rule is if you hear an alarm in
the Hall don’t go in and/or get out.
2.1.1.1 General protocols for fire alarms
discussed.
2.1.1.2 Larry Cardman suggests that alarms
be installed in the tunnels (for all
Halls) so that people approaching the
Hall can’t miss the alarm.
2.1.2 Working through installation list for this
week.
2.2 James Proffitt reports:
2.2.1 Controls of Dynapower (Dipole) power
supplies have been simplified. Should be
easier to operate and look more like the
quads.
2.2.2 Putting together a list of control jobs
for August.
2.2.3 Measured Dynapower control loads on UPS’s
to be 40% of capacity. Have had no power
dropouts since repairing UPS’s.
2.3 A. Gavalya reports:
2.3.1 Discussion of urgency of need for raster
shielding. Can get it sooner but will cost
twice as much.
2.3.1.1 Bob Michaels says it can wait till
September
2.3.1.2 Kees says don’t go out of your way
to hurry it along.
2.4 Kees de Jager asks if anyone has hard
information on the dimensions of the
collimators. No one does. Calling Eddy
Offermann is suggested. Plan is to measure them
in situ.
3 Detectors: (Bogdan Wojtsekhowski)
3.1 Biggest problem during 89-003 was HV failure.
Preparing a backup to speed recovery from
future failures.
3.2 Aerogel is moved aside, clearing the
acceptance.
3.3 This week:
3.3.1 Testing VDC’s for gas leaks
3.3.2 checking PMT’s for light leaks
3.4 Notes that background in the Hall was very high
during Møller Polarimeter tests (4 microamps
beam with Møller produces the same background
as 70 microamps during Oxygen experiment.
Suggests local shielding downstream of Møller
dipole. Some discussion followed.
3.5 Report on studies of efficiency of Burle 8854
PMT’s (used in the Gas Cerenkov) by Matt
Shepherd.
3.5.1 Show layout of test equipment. Flashing
LED through filters gives 1-2 photons at
the photocathode.
3.5.2 Showed spectra. 1 and 2 photon peaks
clearly seen.
3.5.3 Relationship between efficiency, voltage,
and threshold setting puzzling.
3.5.4 Future plans include looking at saturation
effects.
4 Waterfall and 89-003: (Meihua “Meme” Liang)
4.1 Checked data from surveys during Oxygen
experiment. In general our team got better
results than the survey group.
4.2 Started data analysis. Showed Waterfall target
thickness vs. pump speed results. All three
foils have same thickness within error bars.
5 Cryotarget: (Jian-Ping Chen)
5.1 Finished welding two loops. The third is on the
way.
5.2 Upstream windows are prepared and ready for
soldering.
5.3 Window block is machined.
5.4 Transport fixture design is almost complete.
5.5 Solid target ladder:
5.5.1 Ordered more BeO and Carbon targets
5.5.2 Stated plan was to have C, BeO, Al, empty,
and survey targets in the ladder.
5.5.3 Bob Michaels asks for special raster
commissioning targets (2 & 1 mm square
holes)
5.5.3.1 Larry Cardman suggests some kind of
wire mesh target.
5.5.3.2 Ed Folts asks if we can take out
the mechanical solid target actuator.
Yes, but save it carefully.
5.6 Temperature sensors installed.
5.7 Cross calibration of temperature sensors shows
absolute agreement to better than 0.2 K.
5.8 Power supply tests underway
5.9 Valve control electronics assembly underway.
5.10 Preparing cabling and wiring schematic.
5.11 Still on track for 11 August.
6 DAQ: (Bob Michaels)
6.1 Trying to finish CODA 2.0 installation.
6.2 Parity Helicity flipping scheme almost
finished. Larry Cardman suggests that Bob make
sure everybody (Charlie Sinclair) knows what’s
happening.
6.3 Commissioning plan for the raster is written
up.
7 Beamline: (Arun Saha)
7.1 Gold plated Be foils are in.
7.2 Further discussion of Raster targets. Should
get them.
7.3 Accelerator has asked for summaries of work
done in the end stations during shutdowns. Kees
is concerned about the level of detail they
want. Will require further discussion.
7.4 Report from Fast feedback meeting:
7.4.1 Plan to start with 360 Hz. system
7.4.2 Should be operational in Halls A and C
after September shutdown.
7.4.3 Will go to higher frequency later.
8 Optics: (John LeRose)
8.1 Installing new 3rd Order TRANSPORT at CEBAF. Has
some nice new features.
9 Controls: (Javier Gomez)
9.1 Working on spectrometer positioning encoders.
10 Beam Current Monitoring: (Branko Vlahovic)
10.1 Shows history of calibration coefficients over
June.
10.2 A few measurements seem way off. Traced to
occasional bad voltmeter readings. Working to
eliminate.
10.3 Month long average values look very good.
Recommends using them. Should give 0.5% .
11 New People:
11.1 Dave Prout: Post-doc from Kent State.
11.2 Armen Ketikyan visiting for 6 months from
Yerevan.
-JJL