[Bteam] Notes from Yesterday's B-team meeting
Arne Freyberger
freyberg at jlab.org
Thu Oct 22 08:48:46 EDT 2009
B-team Meeting Agenda (2:00pm Wednesday MCC conf. room)
1 2009-10-21 Wed 14:00 Agenda
1.1 Compton Status Happex III
What is the status of the electron and photon compton signals after the
last injector optimization?
* Photon counting
o Injector tuning on October 15th
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1492644>
resulted in good photon rates. Compton photon rates are very
sensitive to the settings of the injector.
o Retune required on October 19th
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1493141> to
get photon rates back to acceptable.
-- orbits were adjusted -- capture gset by 2 out of 6000 --
increased prebuncher by 0.02 -- capture phase by 1.3 degrees
-- A laser phase by 0.5 degrees
o new spectrum look similar to old spectrum (for my crude eyes)
* Electron counting
o electron data appears to be a bit cleaner.
o electron detector moved closer to the beam (about 6mm).
o zero crossing clearly observed.
* Flash ADC photon data
o 1800V operation except when beam conditions degrade and the
things trip off.
o Low photon rate count (number available to MCC) is not a
guarantee that the flash ADC spectrum is clean.
o MCC has no way to know if beam quality is good enough for
the flash ADC analysis.
* Summary
o beam quality is good for photon compton
o electron detector still has a high level background. But
there might not be enough time to address this. Cleaning the
electron background is not as high priority as accumulating
statistics.
* Q/A
o most sensitive signal is a PMT current.
1.2 Injector optimization for Happex-III Kazimi Reza
What knobs are best? Stability and drift? Additional parasitic monitors?
* Continuously monitor the time of arrival at the YAO cavity. Reza
is exploring continuous readout of the 6GHz bunch length cavity to
look for changes in the arrival time at this point.
1.3 Hall-A Transport optics Ryan Tief
What did ray-trace tell us about Hall-A optics?
* horizontal pseudo phase space looks reasonable through the Hall-A
line
* vertical mis-match at the beginning of the A line
* IP02A BPM area significant distortion to the ray-trace ellipse
* distortion is correlated with beam loss in the A line. So scraping
is causing the distortion which starts in the compton chicane. The
ellipse excursion in this region is of order 1.8mm full width. So
there is a tight 1mm vertical issue at the front end of the
compton. The distortion shows up on the negative side, so the
tight aperture is below the beam.
* Detail look at the vertical plots, suggests that the problem
resides somewhere between 1C16 and 1P02A. Better data would help
narrow down the source of the problem.
1.4 Energy change
Date
2009-10-29 Thu
Energy(5-pass)
6.068 GeV, symmetric setup.
?_wien
Equal pain, ?_wien =75
?_wien
During first four days when only B is taking beam, ?_wien = 65
Special Request
Vertical spin alignment in Hall-A for two shifts. Hall-B will want
to go to 1-pass beam during this test. PVDIS will want this in the
middle/end of the run, not at the beginning.
* Comments on PVDIS startup
Would like to address the beam quality issues at the beginning of
the run. This includes:
1. phase advance from modulation coils
2. compton photon rates
3. compton electron rates
4. raster size at target
5. FFB setup
6. 85? A current
7. ?_wien
Most of these issues require close collaboration with Hall-A
experimenters since they provide the measurements and Q&A. The
goal is not merely to reach acceptable beam, but to achieve the
requirements with a robust (stable) setup with minimal
compromises. Time invested at the start of the run to get things
right, should pay off over the duration of the run.
* Energy Change Strawman
This will be discussed in more detail at the next B-team meeting.
o defer cathode bake/activation until 2009-11-02 Mon if possible
o Thursday 2009-10-29 Thu
+ A and C go offline
+ ESR T1 turbine swap out, remove FNAL turbine and
install repaired JLAB turbine.
+ radcon survey of A line from 1C16 to 1P02A, search for
hot spots.
+ Helicity board swap
+ energy change to 6.068 GeV. -- review last June test,
is this allsave ok? -- symmetric setup -- watch the
cryoload
+ 5-pass A to dumplette
+ 5-pass B to F-cup
+ 5-pass C to BSY dump
o Friday--Monday 2009-10-30 Fri-- 2009-11-02 Mon
+ 5-pass CW to B, physics
+ 5-pass 5uA CW to BSY dump for stability
+ periodically 5-pass to A dumplette for quad scans with
1C05
o Monday 2009-11-02 Mon
+ 12 hours gun bake/activation
+ MO ? f 12 GeV studies
o Tuesday 2009-11-03 Tue
+ ?_wien =75 change
+ 5-pass to B when possible
+ 5-pass to A -- day shift, injector optimization of
compton rates -- day shift, ray trace collection or
other optics work -- day shift, beam will be high
current for compton
o Wednesday 2009-11-04 Wed
+ 5-pass to B
+ 5-pass to A -- day shift, more beam studies to
optimize compton -- ray-trace -- aperture scans --
matching -- phase advance -- raster setup
1.5 Optics-on-call
Outgoing
Tiefenback
Incoming
Roblin
* Recent Machine issues
o Compton rates -- highly sensitive on injector configuration,
see notes above.
o Power outage -- 9:20pm Tuesday all power was lost on site --
8:30am Thursday still dealing with issues
o FFB in A is sometimes problematic to configure properly
* Upcoming Week
o Hall-B goes to 1-pass (from 5-pass) -- 2009-10-22 Thu 11:00
start change to 1-pass -- 2009-10-26 Mon ??:?? Return to 5-pass
o Brinkman, Director of the Office of Science visits on
[2009-10-28 Wed]. The machine will go to control access for
a tour of the injector. The tour will also visit the halls.
Opportunity for short duration beam studies.
o Prepare for energy change on 2009-10-29 Thu
Date: 2009-10-22 08:47:18 EDT
HTML generated by org-mode 6.31trans in emacs 23
--
Arne Freyberger
Director Operations Department
Jefferson Lab Phone: (757) 269-6268
12000 Jefferson Avenue Pager: (757) 584-6268
Newport News, VA 23606 Email: freyberg at jlab.org
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