Jefferson Lab Weekly Briefs November 18, 2009
Jefferson Lab Weekly Briefs
November 18, 2009
12 GeV Upgrade
The July 2010 scheduled accelerator down is the last scheduled shutdown prior to the six-month down planned for 12 GeV installation starting in May 2011. In order to coordinate with the scheduled electrical outages during the July 2010 down, JLab Facilities Management personnel have added two acquisition packages for civil construction procurements to their FY10 plans. The N&S Linac Power Upgrade, moved ahead from FY11, provides two new 1.5 MVA unit substations – one each at the North and South Linac service buildings to provide power for the new radiofrequency zones for the 12 GeV cryomodules. The new switchgear section, previously part of the FY10 Central Helium Liquefier Utility Upgrade contract, will distribute power to the new 5 MVA unit substations for the CHL #2 compressors.
Overall, the accelerator ran well. During the past week, the experts spent more than two shifts troubleshooting high Hall A Compton noise. The injector was optimized and the Compton counts were much improved. On Thursday, the storm caused a power glitch, which led to a couple of hours of downtime during the swing shift.
This week, FEL staff performed several tests of the optical transport and setup at long wavelengths and continued studies on injector optimization and terahertz, despite minor water seepage in the vault due to November Nor'easter downpours. The team held a planning meeting for actions on the injector during the December-February time frame when the FEL will not be running. FEL staffers have been heavily engaged with the JLAMP proposal, and tasks, responsibilities and timelines have been determined.
A collaboration between Theory Center staff and experimental and theory users from Hampton University and elsewhere has completed a new global analysis <arXiv:0911.2254 [hep-ph]> of quark distribution functions in which the usual kinematical cuts are relaxed, thereby including more data at high values of Bjorken-x. Effects of target mass (TM), higher twist and nuclear corrections are significant at large x, but the extracted distributions are stable to TM model variations as long as higher twists are also included. The behavior of the d quark as x->1 is particularly sensitive to the nuclear corrections, and using realistic nuclear smearing models, the d-quark distribution is found to be smaller at large x than in previous fits with more restrictive cuts.
JLab's Safety Numbers
126 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Nov. 23: Colloquium - State of High-Level Waste and Spent Nuclear Fuel Disposal, CC auditorium, 4 p.m.
Environment, Safety, Health & Quality
Slips, Trips and Falls
To report unsafe surfaces at JLab, call x7400. Also contact your area Safety Warden so that others in the are may be warned.
JLab 25th Anniversary Jacket Liners
Food Drive for Foodbank
Quark Cafe Offers Thanksgiving Feast
Holiday Desserts to Tempt Your Taste Buds