Jefferson Lab Weekly Briefs
November 30, 2011
Hall A is preparing for a possible beam commissioning run to start on Dec. 12, pending the successful completion of the installation in Hall A. This will be minus the polarized proton target, but will allow commissioning and debugging of several new systems on the beamline, as well as the detector systems. Hall A is also finalizing a project management plan for the Super BigBite projects.
In Hall C, the Q-weak experiment completed tracking measurements, made the transition to high-current running and recommissioned the apparatus. With good-quality beam at currents up to 180 microamps, the experiment sees main detector performance as good or better than the first Q-weak run. The beamline is now instrumented with new digital beam current cavity electronics developed by the Electrical Engineering Systems group. The new electronics essentially eliminate electronic noise on the measurement of beam current as a source of uncertainty for the Q-weak measurement. The experiment is also enjoying excellent performance of the Compton Polarimeter, a result of electron detector maintenance and improvements in laser power over the Six-Month Shutdown.
The week started with high-current tuning to the Hall C beam dump. Optics corrections were made to the machine where needed to get ready for the long holiday weekend of beam delivery. There were some difficulties at first in achieving high-current delivery. After some radiofrequency zones were turned off and the orbits were re-tuned, the accelerator performed excellently during the majority of the extended holiday, with the maximum beam current of 180 microamps being delivered to Hall C and up to 30 nanoamps to Hall B. Hall B ceased taking beam on Monday to change out the target, a process expected to take up to two days.
Center for Theoretical and Computational Physics
QCD tells us that a quark knocked out of a proton violently is nevertheless still entangled with the proton through its phase, an intriguing concept that is thought to explain why the so-called Sivers asymmetry observed in semi-inclusive deep-inelastic scattering experiments at JLab and elsewhere is not zero. To check if gauge link operators representing the "phase history" of the quark are responsible for the observed strength of the Sivers asymmetry, nonperturbative methods, such as lattice QCD, are required. A new paper demonstrates that lattice calculations of Sivers observables and related quantities are indeed possible, even if challenging, and presents first results extracted on the JLab computer cluster from existing configurations from the LHPC and MILC Collaborations.
The Electrical Engineering Systems DC Power group took delivery of the first 12 GeV Magnet Power Supply last week. Fifteen more power supplies are due as part of the 12 GeV Upgrade in the present procurement cycle. The alignment group measured the photon pipe that runs from the Hall D tagger enclosure to Hall D; this pipe is 50 meters long. Additionally, the Survey and Alignment group measured a 12 GeV CLAS12 Region 2 Drift Chamber end plate in the clean room. This plate was measured in multiple loading configurations to check for deformation and deflection. The Mechanical Engineering group (Magnet Measurement) continues to measure/inspect the new magnets for the 12 GeV spreader and recombiners.
Facilities Management & Logistics
There will be a power outage for much of the JLab campus during the winter holidays/shutdown days, from 5 a.m. Friday, Dec. 23, through 6 p.m. Sunday, Jan. 1. The power outage is necessary for several planned maintenance and construction activities. The following facilities and areas will be locked and inaccessible during the power outage:
Power is scheduled to be restored and systems back online for normal operations starting at 7 a.m. on Monday, Jan. 2. The power outage will not affect the ARC, VARC, Buildings 13 and 19, Guard Post 2, the RadCon buildings and trailers or the Accelerator Site. More information regarding preparations for the shutdown power outage will be available on Insight in the coming weeks. For questions regarding the power outage, contact Paul Powers.
JLab Calendar of Events
Dec. 5: Safety Shoe vendor onsite
Environment, Safety, Health and Quality
Walking Surfaces & Cold Temperatures
Computing and Networking Infrastructure
Internet Outage Scheduled for Dec. 6
Computing Services Outage Will Precede Shutdown Power Outage
Note that because outages of the central computing systems are rare and there are dependencies on electric work, the time needed to restore all systems to normal operations is only an estimate.
Many systems across the lab do not recover from a central services outage without human intervention. Work center supervisors and/or building custodians who have essential systems that require human intervention to restore should make arrangements with Facilities Management & Logistics before the holiday break begins. FM&L contacts include:
Once computing services are re-established, individuals should be able to access most computing services, including email accounts, remotely/from home during the remainder of the holiday break. For additional information about the Computer Center outage, contact the IT Division Helpdesk, x7155, before the holiday shutdown begins.
Mobile Mammography Unit Onsite Next Wednesday
Annual Children’s Holiday Party Set for Dec. 10
Volunteers Needed to Help With Children’s Party
Toys For Tots Toy Drive Underway
Holiday Office Door/Cubicle Decorating Contest Underway
Personal Dosimeter Change Out Set for Dec. 19
Tracking Thomas at JLab
Congratulations this week go to Stephanie Vermeire, who was the first to correctly identify the Nov. 23 location. Honorable mentions go to Michelle Shinn, Jodi Patient, Steve Wood and Doug Higinbotham. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.