[Bteam] No Bteam meeting today, compton tuning all day!!!
Arne Freyberger
freyberg at jlab.org
Wed Nov 11 08:47:42 EST 2009
NO BTEAM MEETING TODAY!! Just a status update
1 2009-11-11 Wed 14:00
There will not be a 2:00pm B-team meeting today. We are about to start
(9am nominal start time) a session of compton tuning. I expect this
effort will last most of the day. Today represents a good chance to
learn about the machine, front to end.
Over the course of the last few days we have had several meetings to
discuss the compton tune and how to approach the problem. In addition
data mining and site visits have been performed to gain a better
understanding of the issues.
The present plan consists of:
* Nominal Injector checks (bunch length, orbits...)
o during these checks the vacuum pumps in the compton region
will be checked in the hall. The vacuum may not be as good
as it should be in this region.
* Use the slits in the injector to produce a 10 ? A *clean beam*.
Where *clean beam* refers to a beam with exceptional timing and
bunch length.
o If the compton rate improves, then we know the problem is
sourced upstream of the slits and is probably a bunch length
issue.
* If compton rate is still bad, check the following:
* 5 MeV orbit
* Swing gang phase a bit to see the sensitivity to energy spread
* Separator check, extract the A beam magnetically. Are the rates
sourced at the separation point?
* Put Hall-A at a lower pass? Are the rates sourced from saturating
magnets?
* anything else??? See white board in control room for latest plan.
2 2009-11-04 Wed 14:00 Agenda--NOTES ATTACH
2.1 Beam status
Assessment after cathode activation and 6.067 GeV spin up
* PVDIS Beam Requirements
Parity beam requirements for PVDIS are captured in the attached
document from PVDIS.
o Charge Asymmetry
OK, met during Happex-III, need to continue the good work
o Position Asymmetry
OK, met during Happex-III, need to continue the good work
o Compton Tune
PVDIS would also like to achieve a 1% absolute polarization
measurement. Too achieve this, compton photon rates must be
kept below 100 cnts/? A. Nothing was discussed about the
electron side of the compton. The implications are that the
Hall-A line optics should be robust. Robust: Matched,
understood beam transport in compton region, acceptable beam
size at target and acceptable raster pattern size.
The electron arm of the compton was not fully
operation/understood by the end of Happex-III. How much time
will be required for this effort during PVDIS? Is this a
priority?
o Phase advance
Modulation coils will be used to measure the transfer
function to the A target. Present plan is to use the same
procedure as Happex-III. Discussion of going beyond the
Happex-III approach of exciting coils individually took
place. Attendees from PVDIS did not object to the concept of
driving a pair of corrections, however the owner of phase
advance monitoring for PVDIS was not present and has
objected in the past to simultaneously driving modulation
coils in pairs.
o Beam Matching/transport in the A-line
Attempt to measure the incoming beam parameters Wednesday
were unsuccessful due to a failed harp at IHA1C05. Access
will be made on Thursday to replace the pre-amplifier.
2009-11-06 Fri harp was repaired on Thursday and good data
was acquired Thursday before the Hall locked up. See the
elogs: TWISS/? measurements
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1497094>,
Beam transport with current optics and measured input
conditions
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1497121>
Match results
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1497120>
o Vertical Transverse Spin Component
Must be less than 2%. This will be nulled out during a 2hr
set of Mott measurements. We will not be able to monitor
this during the run.
o Horizontal Transverse Spin Component
?_Wien is set split the polarization equally to A and B. Due
to this running configuration Hall-A has requested and
Physics has approved two shifts of purely transverse spin
alignment. During this setup Hall-B has requested to change
from 5-pass to 1-pass for more low energy calibration. The
total time for this test are as follows:
+ 2 hours Hall-B pass change
+ 8 hours injector work to setup purely (horizontal?)
transverse polarization
+ 16 hours Hall-A data collection
+ 4 hours return injector to nominal configuration
+ 2 hours pass change for Hall-B
Four shifts in total. Scheduling of this is to be discussed
over the next few weeks. Hall-A is leaning to desiring this
run in a few weeks, Hall-B wants to defer this as far into
December as possible (They want to put some time between the
1-pass running they just finished and the next round).
o Raster size
This will be an issue for PVDIS. No requirement presented at
the meeting.
o Bob Micheals summary
PVDIS parity requirements achieved during the Happex-III
running. Energy measurement of 150nm at 1C12 appears to be
some noise source in the machine. Large spread might be due
to interception at the injector. Noise is speculated to be
amplified when running with a closed slit for the Hall-A.
The commissioning plan for PVDIS can found here
<http://hallaweb.jlab.org/experiment/E05-007/documents/runplan/draft.html>.
General PVDIS information can be found here
<http://hallaweb.jlab.org/experiment/E05-007/>.
* Bonus Beam Requirements
o Any issues with Hall-B beam?
Beam size and halo requires as usual for Hall-B ?_x , ?_y <
150 ? m. Bonus will run a unusually high beam current (up to
200nA) for Hall-B. This has the benefit of allowing the
typical SEE BPMs to work so we will be able to monitor
Hall-B orbit during most of the run.
2009-11-06 Fri
The Hall-B beam size has not be repeatable across
accelerator activities (Injector work, control accesses). A
good beam spot can be achieved, but it is disconcerting to
loose time establishing a good tune every time something
changes in the machine.
* Spin dance
Hall-A is measuring 83% Hall-B is measuring 81%. This suggests
that ?_Wien is set very close to the optimum point. Typically
Hall-A M{\o}ller measures slightly higher polarization than the
Hall-B M{\o}ller. More M{\o}ller runs are planned over the next
few days which will provide more information as to the present
configuration and the need for the spin dance.
Both A & B are at 5-pass, so the machine configuration options are
limited to adjusting ?_Wien so that P_A = P_B .
o TODO Make a decision about Spin Dance before Monday morning
HallB HallA
DEADLINE: 2009-11-09 Mon
2.2 General Discussion
* Parity requirements achieved for Happex-III and PVDIS
* energy spread achieved for HKS, HKS completed with a large
fraction of the expected data.
* Bonus is fully commissioned
These accomplishments were difficult and have strained the staff. What
can we do better? Things I'd like to discuss include:
* B-team
o more involvement from Physics? Yes, everyone agrees that
more communication is better. Arun (Hall-A), Stepan (Hall-B)
and Gaskell (Hall-C) will be added to the bteam mailing list.
We will also try to organize the B-team meetings such that
Hall specific items are during the first portion of the
meeting.
o less Wednesday meetings, more daily 8:15 meetings No and yes.
o B-team content
o Goals for FY10? -- 12 GeV commissioning plan -- PREX parity
quality -- QWeak parity quality -- Information
transfer/cross training -- TWISS/? measurement and matching
routine -- raytrace data collection and analysis routine for
beam physicists
* 1:30 scheduling meetings
o Low attendance
o Little information transfer
o Summary
The 1:30 scheduling meeting serves a different purpose than
the 8am meetings. However the 1:30 meeting has become too
static. Need to figure out how to make the meeting a bit
more animated.
* Beam Studies
o C50 commissioning has resulted in almost no beam studies
being performed.
o No more C50 commissioning during physics operation
o Double Wien commissioning during physics operation
(Spring10) looks to be just as disruptive. -- working with
Whitney to see if Homeland security run can be move to
July2010.
2.3 Optics-On-Call
* Outgoing Byunn Yung
* Incoming Yuhong Zhang
Date: 2009-11-11 08:44:15 EST
HTML generated by org-mode 6.32trans 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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