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Archived Messages for HALLA_MIN_1997@cebaf.gov: Minutes
Minutes
John LeRose (lerose@CEBAF.GOV)
Thu, 24 Jul 1997 14:53:18 -0400
Minutes of Hall A Group Meeting 22 July 1997
1 Run report 89-033: (Paul Rutt)
1.1 Setup went well
1.2 Since last Thursday beam availability was about
30% with DAQ going on for about 27% .
1.3 New controls and documentation working out well
1.4 Problems:
1.4.1 Q2 Hadron having infrequent cryogenics
originated trips.
1.4.2 CHL down since 9:40 yesterday (21 July)
Present hope is to have things cold by
17:00 today and have beam in the Hall by
20:00 this evening.
1.5 Discussion of need to make an access to check
status of AC in the shielding hut. Plan is to
open hut and check at 15:00.
1.6 Simultaneous measurement of beam polarization
with Mott and Møller polarimeters achieved
1.7 ep made some preliminary measurements.
1.8 Ed Brash reports on Data Analysis:
1.8.1 Looking at H(e,e’p) had about 20 million
events by Sunday (20 July) night.
1.8.2 Showed azimuthal distributions after
filtering. Conclusions were:
1.8.2.1 Alignment parameters are very close
to correct
1.8.2.2 Reproducibility from commissioning
runs looks very good.
1.8.2.3 Measured beam polarization to be
0.38±0.013
1.8.3 Review of CPU time needed to analyze shows
that data analysis should be able to keep
pace with data taking.
1.9 Dan Dale reports on Møller Polarimeter
commissioning:
1.9.1 Last week’s charge reading problems have
been cleared up. Starting to get
reasonable numbers for the measured
asymmetry.
1.9.2 “Spin Dance” done to check for correct
spin injection angle to give longitudinal
polarization in the Hall. Determined
correct angle to be -41º. Expected value
was -51º. Implication is that the beam
energy may be 0.25% lower than thought.
1.9.3 Things to do:
1.9.3.1 Seeing discrepancy between
measurements with target polarization
parallel and antiparallel to beam
polarization . Need to clear this up.
1.9.3.2 Work on shielding improvements.
1.9.3.3 Optics studies.
1.9.3.4 Studies of measured polarization
vs. spot size, current, target
heating, and tune.
1.9.3.5 Hodoscope studies.
1.10 Yves Roblin reports on ep measurements:
1.10.1 Took 2 runs.
1.10.1.1 1st at 2.5 microamps got 100
events with 40 of them real. Need to
work on tuning electronics.
1.10.1.2 2nd still being analyzed.
1.10.2 Expect a more thorough report next week.
1.11 Arun Saha reports on preliminary results of
radiation monitoring in the Hall. Møller target
makes significant increase in background. But
not so much to be a problem as far as our
radiation budget is concerned.
2 Installation/Engineering:
2.1 Ed Folts reports:
2.1.1 He’s staging for the August shutdown
(12 August - 19 September). Things already
look tight. Get requests into him ASAP.
2.1.2 Question re raster readiness. Bob Michaels
says all parts are ready. Kees says it’s a
must for August. Some question on
readiness of table.
2.1.3 Meme wants the solid BeO target measured.
2.2 Paul Brindza reports:
2.2.1 The transport fixture for the target
contract has been awarded and should be
here 8 August.
2.2.2 Design of solid and dummy target
extensions were done today.
2.2.3 Design work ongoing on alignment systems
2.2.4 Will check on status of raster table.
2.3 James Proffitt reports:
2.3.1 Electron Q3 power supply is having
problems. Spurious voltages in the leads
causing trips during ramp up. Temporary
fix is to reduce ramping voltage to 1
Volt. Will have to address in more detail
in August. Will limit high current
operation if not repaired.
2.3.2 Flow indicator switch has failed on Hadron
Q1.
2.3.3 Written report available on Lakeshore
(Møller quad) fault problem.
2.3.4 Last weeks problem with failed motor on
Hadron arm was a bad optical encoder.
Problem has repeated itself this week on
the Electron arm at the same time as the
flow indicator problem on Q1 Hadron came
up. James speculates that radiation damage
may be the root cause. Kees says this will
have to be studied further.
3 Controls: (Javier Gomez)
3.1 Working on Deuterium experiment.
4 Detectors: (Bogdan Wojtsekhowski)
4.1 Scintillators OK.
4.2 Found and repaired bad solder joint on VDC
4.3 Gas Cerenkovs:
4.3.1 Installed new set of PMT bases. Number of
photo-electrons is the same (7-8)
4.3.2 Efficiency of PMT’s is stable at 1% level
over a fair range of voltage.
4.3.3 Base modifications have improved relative
efficiency about 5%
4.4 Detector geometry measurements have been
completed by two High School teachers, Al
Kaufman and Neil Jenkins. Full report next
week.
5 DAQ: (Bob Michaels)
5.1 Working on event readout for fast raster and
BPM.
5.2 Dave Abbott reports on CODA 2.0:
5.2.1 Overview presented. Similar to CODA 1.4
but more flexible.
5.2.2 Reviewed over structure and various
components. Highlights include:
5.2.2.1 More object oriented
5.2.2.2 MiniSQL database
5.2.2.3 Data Distribution (DD) scheme.
5.2.2.4 Message logging using cmlog.
5.2.2.5 More configurable parameters (good
and bad, if you don’t know what
you’re doing you can mess things up)
5.2.2.6 New Readout Controller (ROC)
5.2.2.7 2 component run controller,
rcserver and runcontrol (GUI).
5.2.3 Runs on Solaris, adaqs1.
5.2.4 More information is available on web site
(http://alcor.jlab.org)
5.2.5 Still under development. Functions are
fixed but are trying to make it more
robust.
6 Spectrometer Optics and Magnets: (John LeRose)
6.1 Working on improved TRANSPORT model of
spectrometer for Deuterium experiment.
6.2 Evaluating multiple scattering at exit of
spectrometer and possible improvements. Thinner
Mainz style window helps a lot. Helium between
VDC’s helps some more. More details next week.
6.3 Reviewed status of our understanding of the
location and shape of the Collimator/sieve
boxes on the spectrometers.
7 Cryotarget and Compton Polarimeter: (Jian-Ping Chen)
7.1 Cryotarget:
7.1.1 Welding is completed on loop piping.
7.1.2 Loops have been pressure tested.
7.1.3 “Beer cans” soldered to cell block
7.1.4 Working on soldering of upstream window to
cell block.
7.1.5 Loops have been completely leak checked.
7.1.6 Vapor Pressure Transducers (VPT’s),
Temperature sensors, and low powerheaters
have all been installed
7.1.7 Testing pump driver and tachometer
readback.
7.1.8 High power heater remote control box
assembly is finished. Now testing.
7.1.9 Software development going well. (High
School teachers have helped with software
and documentation)
7.2 Compton Polarimeter:
7.2.1 Ordering 3 BPM’s
7.2.2 Dipole power supply cabling scheme checked
with safety and is OK.
7.2.3 Will use heating foils to bake vacuum
pipe. Need to know if there is enough
208V AC to handle additional 10 KW.
7.2.4 Worried about vacuum level in beam pipe,
1E-06, at ep. Will need 1E-08 to 1E-09 at
Compton Chicane.
7.3 Notes there will be a polarized 3He meeting
next Friday and Saturday (25-26 July)
8 Assorted announcements: (Kees de Jager)
8.1 Dry runs for PAC proposals will be held on
Thursday 31 July. All are invited.
8.2 Scheduling committee will meet this week to
adjust the existing schedule to accommodate 2
Hall operations.
8.3 Re the proliferation of pagers:
8.3.1 Upon announcement of the subject all staff
immediately volunteer to turn in their
pagers. The offer was declined.
8.3.2 There is a supply of “floating” pagers for
running experiments. Rachel Harris is the
custodian of these pagers.
8.3.3 People here for short periods can get a
temporary pager from the pool of floating
pagers. These must be returned when you
leave.
8.3.4 Users who will be here more than 60% of
the time can get a permanent pager if they
need one.
Clarification: re parking announcement at last week’s
meeting and as reported in the minutes. Larry Cardman
writes:
In the minutes you noted (as Javier no doubt
reported) that "all users and staff are urged to not
park in the designated 10 minute parking area in
front of CEBAF Center for more than 10 minutes." To
be more precise (because there appears to have been
some confusion on the issue) the parking in question
includes anywhere in the "circle" in front of CEBAF
Center - ie it is NOT OK (as some seem to think) to
park in unmarked spots there. Further, as a general
rule, the lab wants to keep those spaces available
for visitors and those doing drop offs and pick ups
at the lab during working hours. During working
hours a simpler rule of thumb would be simply "don't
park in front of CEBAF Center."
Larry
-JJL