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Archived Messages for HALLA_MIN_1997@cebaf.gov: Minutes
Minutes
John LeRose (lerose@CEBAF.GOV)
Thu, 09 Jan 1997 14:46:09 -0500
Minutes of Hall A Group Meeting ,7 January 1997
1 Kees de Jager welcomed as new hall leader. The meeting will be run for the
last time by Larry Cardman. Kees will start running the meetings next week.
2 Hadron Dipole Report: (Larry Cardman)
2.1 Present best guess as to what’s wrong is that there is a short
(R=9.5 milliOhms) across one of the four pancakes in the coil package.
2.2 The superconductor is intact.
2.3 The still open question is: Can we live with it?
2.3.1 James Proffitt has added EPICS monitoring to all available
information during operation of the magnet.
2.3.1.1 He levels
2.3.1.2 Temperature
2.3.1.3 Lead Flows
2.3.1.4 Voltages
2.3.1.5 Current
2.3.2 Are running series of tests in which the magnet is run up to set
currents (in 100 Amp steps) allowed to stabilize and the put
through a slow dump. As of yesterday we had gotten to 500
Amps with no problems.
2.3.2.1 Have observed spikes in lead flows and He levels that
correlate well with ripples in current and voltages
during discharge. The theory is that during the
discharge mutual induction effects between the shorted
and unshorted coils induces a rise in the current in the
short which warms it up, causing He boil off and an
increase in its resistance. The increased resistance leads
to a reduction in the current through the short which
then allows it to cool, lowering its resistance, and the
cycle continues as the magnet discharges.
2.3.2.2 Still don’t know how far we can push things.
2.3.2.3 Have no real understanding of how the short came
about.
2.3.2.4 Observed characteristics appear to be stable.
2.3.2.5 Expect to have enough information to make a serious
stab at answer whether or not we can live with it in a
week or so.
3 Engineering: (Ed Folts)
3.1 Putting in final touches to fire suppression system in the shielding huts
3.2 Getting ready for Cryotarget platform installation
3.3 Preparing to install large Kapton window on scattering chamber
3.4 Expect delay line installation to be finished this week.
4 Commissioning: (Eddy Offermann)
4.1 Showed comparison of first order transfer matrix elements as
calculated by John LeRose using RAYTRACE and his best knowledge
of the fields and locations of all the magnets for our “standard tune”
with results of the sieve slit measurements. In general agreement is
very good. Still not sure of the exact location of the slit.
4.2 Re measurements at 845 MeV just before Christmas. Data is not as
good as we hoped for. Beam spot moved during the run and we didn’t
know about it.
4.2.1.1 Had problems getting computer display of Beamline
diagnostics to work.
4.2.1.2 Arun says the problem is fixed.
4.2.1.3 People in accelerator didn’t know we cared about
where the beam spot was.
4.2.1.4 Suggested that beam location information be archived.
4.2.1.5 Suggested that we set up an alarm for when the beam
moves outside acceptable parameters.
5 Chamber Gas: (Howard Fenker) Going over punch list items for system. No
outstanding problems.
6 Beamline: (Arun Saha)
6.1 Pierre Bertin reports on plans for installation of ep beam energy
measurement system.
6.1.1 Showed schedule. Expect arrival at JLAB 19 January.
6.2 Larry notes that it has been announced that the accelerator startup has
been delayed for two weeks.
6.3 Re Arc Beam Energy measurement. (Pascal Vernin reports)
6.3.1 Super harps are here and installation plan is in place.
6.3.2 There are eight people here from France who had planned to
sty until 15 February anticipating with beam tests. They will
have to change plans to accommodate the accelerator schedule
change. Pascal asks that dates be as fixed as possible. Larry
suggests that Pascal attend scheduling meeting one from next
Thursday (i.e. 16 January)
6.4 Current Monitoring: (Branco Vlahovic reports)
6.4.1 The noise problem in the cavities has been solved. There was
an error in the software. Noise is now about 1 nanoAmp.
6.4.2 Time fluctuations in the Unser monitor are correlated to the
heater cycling.
6.4.3 Plan to move the hardware downstairs in order to shorten
cables discussed.
6.5 Arun has had meetings with survey people re spectrometer positioning.
Written report will be circulated.
7 Hadron Detector Electronics and Waterfall Target: (Meihua “Meme” Liang)
7.1 Waterfall target ran successfully with no problems in December run.
7.2 Target thickness tests being studied
7.3 Noted problem with runtimes being recorded consistently. Will be put
into the data stream soon.
7.4 Showed preliminary results of luminosity monitor tests.
8 DAQ: (Bob Michaels)
8.1 Script for writing data into silos is available.
8.2 Working on Fastbus test stand. Dave Abbott is working on problems
with the Fastbus controllers.
8.3 Instructions for using the detector map will be distributed via e-mail
8.4 Computer reorganization discussed
8.5 Extra cabling will be needed for coincidence measurements. Will need
to organize a cable pulling party.
8.6 Working on Pb Glass calibration.
9 Cryotarget: (Jian-Ping Chen)
9.1 Gas platform installation to start next week.
9.2 Joyce Miller finishing design work on target.
9.3 Techs working on cell fabrication
9.4 Students and post docs:
9.4.1 Voltage divider circuit box completed
9.4.2 Power Supply frequency controller tested successfully.
9.4.3 Readout boxes for temperature sensors being tested
9.4.4 Software being developed
9.4.5 Solenoid control electronics
9.5 Next week French collaborators working on the Compton Polarimeter
will be here. Arun Saha asks that they specify their radiation level
requirements.
9.6 Magnet power supplies will be located on bldg. 98
10 Controls: (Javier Gomez)
10.1 New control software in plane for electron and hadron arms
10.2 Drivers for beam charge monitors are finished.
11 Detectors: (Bogdan Wojtsekhowski)
11.1 Working on calibration of shower counters using cosmic rays. (may
not need flash calibration)
11.2 Expresses concern for high local rates in VDC’s during elastic
scattering runs.
11.3 Gas Cerenkov is ready. Will need 1-2 shifts for commissioning.
11.4 Working resolution analysis for S1/S2
11.5 Hadron arm basic package is still in good working order. Will be rolled
out to allow work on FPP but should pose no problem to have in place
and ready to run 14 February.
12 Møller Polarimeter: (Sirish Nanda)
12.1 Working on checklist for installation
12.2 More next week. Planning a review of vacuum system.
13 Seminar Committee: Eddy Offermann’s tenure is up on the committee. A
replacement is needed. No one volunteered. Larry leaves this one for Kees to
deal with.
-JJL