Jefferson Lab Weekly Briefs
May 18, 2011
PhysicsLast week, Hall A completed the short-range correlations experiment on Friday. Hall staffers are entering the six-month shutdown with a big list of work items to prepare for the g2p/GEp experiments.
The Q-weak experiment in Hall C completed a six-month commissioning and initial data taking run, acquiring an estimated 30 percent of the proposed data. The reliable target performance and excellent accelerator operations allowed the experiment to commission the detectors and Compton polarimeter, begin data taking, and learn lessons for the next run. Q-weak will run for another six months, starting in November.
AcceleratorThe CEBAF accelerator operations crew terminated beam operations for FY11 on May 13. The CEBAF acclerator has been operating continuously since the beginning of the fiscal year in October, with only the short winter break at the end of December. The final week of operations was occupied with beam delivery to Halls A and C and many beam studies. The beam studies targeted the even arc dipole field gradients; these dipoles will be modified during the six-month shutdown, and these measurements will help resolve any difficulties with beam restoration after the shutdown. Beam studies were also used to characterize the 2L21 cryomodule for comparison to the new cryomodules being characterized in the Test Lab. At 7 a.m. on May 13, beam was terminated and the shutdown began. Thanks to everyone who participated in FY11 CEBAF operations!
Free-Electron LaserThe FEL group continued multi-kilowatt running into last weekend and completed the high-power run on the oxide-coated outcoupler. This week, the team successfully completed the planned set of tasks for the Air Force, while running pulsed laser deposition experiments on swing and partial owl shifts. The FEL has now shut down for installation of a new low-conductivity water system.
Theoretical and Computational PhysicsA new theory paper <arXiv:1105.2764> explores the possibility of incorporating the Roper resonance into chiral perturbation theory (ChPT), a low-energy effective theory for QCD that in its quintessential form includes only the pion and the nucleon. Although it is expected that the Roper would improve the long range interactions in the π N system, the fact that the Roper-nucleon mass splitting is large may jeopardize the convergence of the low momentum expansion in ChPT. This article investigates the effects of the Roper on low energy π N scattering and discusses the profitability of including the Roper as an explicit degree of freedom in ChPT.
EngineeringThe alignment group (Metrology) is surveying the west and east arc dipoles and many of the quadrupole magnets in support of the six-month shutdown. The magnets' current positions must be found (to better than 0.25 millimeter). Over the years (originally installed 1992-1994), the tunnel has shifted slightly, and the magnets have also shifted due to this movement and probably also due to cycles in temperature of the supports. The magnets will be refurbished and have ‘H’ steel added. Following this procedure, operations personnel want the "as-found" magnet positions re-established to reduce the amount of changes they will have to make to thread the beam through the magnets on its path to the end stations.
Additionally, alignment is carrying out a precise survey in the northeast corner of the accelerator, where there is excavation to extend the north linac to the new Hall D tagger building. This activity will be used to monitor any movements that may occur in the tunnel and the magnets due to the removal of the earth covering the existing tunnel and the actual construction. If any movement is detected after construction, the magnets will have to be re-aligned in this area.
Precision levels are also being done throughout the accelerator to update the existing alignment control network, and two cryomodules will be aligned for test purposes in the next few days.
The majority of the 'H' steel has arrived onsite. The ‘H’ steel will be added to the dipoles pulled from the tunnel. The magnet group has completed refurbishment trials for the BB (two-meter) and BA (three-meter) dipole magnets. The baseline magnetic measurements have been completed for the BB and BA magnets.
The vacuum chambers and synchrotron radiation coils were installed on 31 four-meter XP dipole magnets. Stretch wire measurements were completed on these dipoles. Twenty eight of the XPs will be installed in the tunnel during the six-month down.
Other tasks completed by the magnet group were the completion of the six month refurbishment schedule, building new fixtures for the stretch wire measurement tables and upgrading the hall probe holding fixture for detail grid measurements.
Environment, Safety, Health and QualityCritters, Bugs and Reptiles On the Prowl at JLab
JLab shares its grounds with an array of wild creatures, and recent construction has disturbed the natural habitat of many. The ESH&Q Division and the Facilities Management and Logistics Department urge everyone to take precautions when working in areas that mimic or overlap the natural habitat of native creatures. These precautions include:
If you are stung or bitten, report to Occupational Medicine. Prompt medical care can help prevent infection and complications that could result in unnecessary pain and lost work time.
Computing and Networking InfrastructureMaintenance Day Scheduled for May 24
The IT Division's CNI group is planning a maintenance period on Tuesday, May 24, 5-10 p.m. During this time, staff and users may experience some short network and web server outages (should be less than 15 minutes in length). Additonally, the group will push out Linux and Windows patches, so plan on rebooting your system as soon after Wednesday morning as is convenient. If you have any questions, contact the IT Division Helpdesk, x7155.
AnnouncementsMont on Big Numbers
The latest Montage has been posted to the JLab website. Montage is an ongoing series of articles about issues affecting the lab written by JLab Director Hugh Montgomery. Click the link for Montage or access it via the JLab homepage.
Library Is A'Changing
The JLab Library will be reconfigured in the coming weeks. This change, prompted by the increasing need for space at the lab, will give the library a smaller physical presence and accelerate the shift to a more electronic and interactive library. From now until May 25, staff and users should mark important books that should be kept by the library. For more information about the marking procedure, contact Sandra D’Souza, x7524. For more information, visit the JLab Library webpage.
Book Swap Lunch Party Planned for Friday, May 27
Are you looking for your next great read, but still have a collection of books you're ready to pass on? Then kick off the Memorial Day weekend with a good, old-fashioned book swap! If you'd like to participate, just bring no more than 12 of your gently read books to CEBAF Center F113, noon-12:15 p.m., on May 27. You'll get a voucher for the number of books you bring in. All books will be grouped by genre. New book selection starts at 12:15 p.m., and you may take away as many books as you bring in. Swap ends at 1 p.m. Any un-selected books will be placed on a bookcase in CEBAF Center for sharing to continue. All non age-restricted genres are welcome, including sci fi, fiction, self-help, fantasy, children's, romance, cookbooks and etc. For more information, contact Kandice Carter, Maya Keller or Deb Magaldi.
Tracking Thomas at JLab
Little Thomas is visiting all corners of the JLab campus. If you can identify his location this week, email Kandice Carter with your guess. The first correct response will receive special recognition on this page. Guesses are accepted through Fridays.
Congratulations to Kevin Jordan, David Fazenbaker, Jason Willoughby and Debra Brand who were the first people to correctly identify the May 11 location. Honorable mentions go out to Elena Long, Keith Royston, Gina Dixon, Sue Witherspoon, Harry Fanning, Mike Koch, Charlie Garrison, Stephanie Vermeire, Dick Owen, Stephen Smith, Mike Lewellen and Bill Merz. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.
JLab Calendar of EventsMay 17-20: NSTAR 2011
May 23: Safety Shoe vendor onsite
May 30: Memorial Day holiday - JLab closed
May 30-June 18: Hampton University Graduate Studies Program
June 6: Safety Shoe vendor onsite
June 6-8 Users Group Workshop and Annual Meeting
June 20: Safety Shoe vendor onsite