[Bteam] Notes from today's Bteam meeting
Arne Freyberger
freyberg at jlab.org
Mon Sep 28 14:52:25 EDT 2009
B-team Meeting Agenda (1:30pm Monday MCC conf. room)
1 2009-09-28 Mon 13:30 Two things
I'd like to have a meeting *today* at 13:30 to discuss the HKS energy
changes and the Happex-III phase advance.
* HKS energy changes
o Physics consensus on the allotted amount of time Arne
Still no word from Dennis on the agreed upon time allotment.
2009-09-28 Mon 14:48
This just in from Dennis
Dennis:
I talked to Nue some more. He would be willing to go down to one
major energy change (+20MeV), but get more statistics. It doesn't
save much time , but reduces risk because of fewer energy changes.
So the request looks like
Pulsed beam 2hr (spacing between micropulses to do Time of flight studies.)
+1 MeV 4hr (including tuning)
-1 Mev 4hr (including tuning)
+20Mev Tune 4hr
+20MeV data 16hr
Restore 4hr
So about 4.25 shifts.
Steve
o HKS desired energy shifts Spata
+ ± 1 MeV shifts
Small ± 1 MeV energy shifts, with the energy
acceptance of the machine. Hall-C does not need high
currents for these energy shifts. four hours of data
taking per point.
Hall-A beam during this part of the test? one-hour to
perform these shifts.
# dial in the shift into the energy lock.
# adjust Hall-C arc dipole to accomodate this
change? No leave dipole strings alone.
# Adjust Hall-A string? Might need to do this
since Hall-A is running at 100?\text{A}.
# FFB in relative mode in C due to the energy offset.
# DW1, DW2 small adjustments to keep beam on dump
viewers.
+ +20 MeV shift
This will require a tune of the entire machine (after
it is scaled). It will go faster if we leave Hall-A
out of the mix.
# splitter stays unchanged
# DW1 goes down
# DW2 goes up
# change dipoles, quads, correctors.
# Raise DZ HMAX, HOPR need more headroom. Needs to
goto 320 Amps.
# Steps
* load scaled allsave, in the special file area
* relem at the new energy
o Schedule
+ Dump pump issues Arne
Presently Hall-C dump pump is broken and Hall-C is
limited to 3.5?\text{A}. The pump will be repaired
sometime on Wednesday.
When the pump is repaired and ready to be installed,
there will be a 2hour interruption to beam delivery to
Hall-C during this period.
The pump will have to fixed before the 20 MeV shift
since HKS wants to run at full current for this
portion of the test.
o Plans
+ Yan to develop ATLIS
+ Benesch to scale the file
o Owner
+ Spata to own the process, review the ATlis, and review
the scaled allsave file
* Happex-III phase advance
o Happex-III requirement Alex Jay
+ Position at 1H04A, 1H04B
+ angle at 1H04A, 1H04B
+ Energy shifts
o Present status Alex Jay
Using various settings of the quadrupoles after the Compton
polarimeter Jay has altered the phase advance for Hall-A. It
has improved, but we are waiting for word if it is good
enough. Presently they have 20 ? radians in horizontal, 8 ?
radians in the vertical plane. Changes are coupled to
changes in the rastered beam size. These two requirements
are often in conflict.
o Hardware
Qweak is moving towards powering two coils simultaneously
with different amplitudes. Hall-A has the same hardware
installed but are not using the coils in this manner. Why
not? Need to write a letter to Kees and Kent. We want to use
the coils as designed for PVDIS and Prex and possibly for
Happex-III.
o Plans if present status is unacceptable
Upon resumption of beam delivery to Hall-A, after C50 work
and HKS energy shifts, we will take a couple of hours to
perform:
+ Ray-trace data through the hall-A line
+ New set of harp data at 1C05
+ ????
o Owner
Jay and Alex will work on this problem. Ryan will help by
collecting the ray-trace data and assisting the analysis.
2 2009-09-23 Wed 14:00 No meeting
There will not be a B-Team meeting today.
* Brief status Report
Machine is running well since last Wednesday transport clean up.
It is unclear if the Compton rate reduction was due to shifting
the doglegs "out of the mud" and fixing the separator, or the
thorough cleaning up of separation and transport lines by MikeS
and Yan. The reason we are confused is due to the fact that the
Compton detector was in a non-standard configuration all day
Wednesday. Nevertheless the machine is in a "good place" due to
all these efforts.
The Beam Loss Accounting system is still has a large amount of
noise, but the transport appears to be clean if one looks at the
Beam Loss Monitors, Beam Scraping monitors, Hall-B harp scans,
Hall-A compton rates. Yesterday the 500KeV kicker sensor was
jumpered out to remove a 80Hz intensity fluctuations in order to
minimize the issues with BLA system. With the this sensor jumpered
out the 80 Hz noise was removed, but the BLA still fluctuates
between 0 and 1.7 ? A of loss.
The main issue this week have been establishing robust FFB
configuration to both A and C. Sometime Monday morning, things
drifted such that disabling/enabling FFB in the A line caused ep
ion chamber trips. By carefully calibrating the FFB response
matrix using low 5 to 10 ? A beam current, the FFB system appears
to be more stable. Scott Higgins, Pete Francis and Yan worked out
the FFB subtleties yesterday.
There was a spurious, unexplained vacuum event in Arc1 earlier
this week. The excursion was not significant enough to close
valves, but three ion pumps reported elated vacuum levels.
o Parity Quality-Happex
Happex is not reported any information on parity quality so
we don't know where we stand on this issue, only that the
user claims there are more pressing issues. The most
pressing issue to Happex is the phase advance at the last
two BPMS, Alex and Jay have some plans to address this at
Happex's request.
o Energy Spread-HKS
Energy spread appears to be reasonably under control. The
OPS crews need to keep running KREST and chase down
pathlength errors as much as possible to keep the energy
spread under control. Without knowing the ?, ? and ? and the
3C12 dipole the exact value for the energy spread is
unknown. The Synchrotron Light Interferometer measures 3.5×
10^-5 , which is an upper limit as long as the ? is near the
design value of 4m.
Beam transport to HKS has been routine over the week, no
issues other than FFB.
o Hall-B
Hall-B finished their experiment this morning and will down
for the next nine days to reconfigure. This experiment
started in the Winter run this year. For this Fall09 run
period Hall-B did not achieve its goals.
* On Call
Reza was on-call last week. This week it is Geoff Krafft.
3 2009-09-16 Wed 14:00 Agenda--Notes
We will have a brief meeting after the 1:30 scheduling meeting to
discuss machine performance, list known problems and possible solutions.
The machine has been running with issues over the week. Hall-A has had a
variable compton rate and the energy spread is not quite good enough for
Hall-C. With that said the Halls are "happy" with the beam quality, but
as the experimental issues subside the accelerator issues will become
more pressing.
The goal of the meeting will be to develop a plans. Execute the
non-invasive plans and lobby for time to execute the invasive plans on
Thursday.
Date: 2009-09-28 14:50:20 EDT
HTML generated by org-mode 6.30trans 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/bteam/attachments/20090928/76bf0fcf/attachment-0002.html>
More information about the BTeam
mailing list