[Bteam] CEBAF status update

[Arne Freyberger]

  NO BTEAM MEETING TODAY!! Just a status update


    1 2009-11-12 Thu 12:35 Status Update on Compton Rate

Yesterday, Wednesday was spent working on trying to understand the 
source of the high compton rates in the A line. There are two good 
elogs, one that explains what was done by 
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1497992?PHPSESSID=ed0145cef7641721110cade5b8cf8765> 
Reza and another interpreting the results 
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1498005?PHPSESSID=ed0145cef7641721110cade5b8cf8765> 
by Tief. In addition there was some effort to tune the Hall-A compton 
line after the injector work which is described here 
<http://opweb.acc.jlab.org/CSUEApps/elog/entry/1498001?PHPSESSID=ed0145cef7641721110cade5b8cf8765>. 


First I'd like to thank Reza and Mike for taking to the time to write 
their detailed entries. Such entries really help document what has been 
tried and possible path forward. Second I'd like to thank everyone who 
engaged yesterday. We are still not where we need to be, but perhaps we 
are on the right path.

This morning the Bteam, Source, and Hall-A (Spata, Benesch, Yan, Kazimi, 
Freyberger, Grames, Suleiman, and Camsonne) met to discuss yesterday's 
results and the path forward.


      1.1 Compton Status

Alex C. reported that after the compton detectors had settled down after 
last night high current run, the 4 to 1 signal to noise ratio returned 
at 10 ? A. So the ability to see a compton signal at low current is 
retained.


      1.2 Comption Region

    * vacuum
      This should be fixed as soon as possible. As of 12:45, the Hall is
      preparing to go into access to work on the vacuum in this region.
    * Clean transport through Compton apertures
      Alex C. was asked to provide some specifications for the beam
      position and angle through the compton. With the requirements,
      some time will be spent to find the horizontal edges of the
      aperture and place beam at the center of the aperture. Last night
      only one edge was found and Happex-III values were about one mm
      from that edge.


      1.3 Intermediate Injector Work

Things to try that are reasonably non-invasive, on Thursday and Friday. 
Hall-A is not requesting Compton Work until maybe Monday.

    * Close the slits
      We may be able to mask the problem by running with the slits
      lightly closed. There will be an additional (say 20%) more current
      drawn off the cathode, but the cathode appears to be robust enough
      to support this. Once the transport has been optimized, this step
      should be tried.
    * Weekend configuration
      Hall-A will probably run over the weekend with what they presently
      have. They will periodically lower the beam current to a value
      that allows the compton to run. Take some data with the compton
      and then go back to 100 ? A.


      1.4 Monday 2009-11-16 Mon

There was much discussion of why the Injector setup is not converging. 
Loss of confidence in the bunch length tool being the main topic, along 
with lack of stability at the front end.

There were several ideas discussed and it was agreed that we need 
another 8 to 12 hours to understand (and hopefully correct) the injector 
setup. This next injector period is tentatively scheduled for Monday. 
Reza,Tief and Grames are to develop the plan.

There was some discussion of revamping BPAM for the Hall-A match. This 
should be pursued in parallel with continue to take data with the 1C05 
harp and trying to understand why the horizontal TWISS values keep 
changing.

Date: 2009-11-12 13:04:20 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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/bteam/attachments/20091112/2368cdb1/attachment-0002.html>