Jefferson Lab Weekly Briefs November 17, 2010
Jefferson Lab Weekly Briefs
November 17, 2010
12 GeV Upgrade
The intermediate manufacturing readiness review for the solenoid magnet and the final manufacturing readiness review for the torus magnet for the Hall B CLAS12 spectrometer were held at the vendor, Wang NMR. The wave-shifting fibers for the pre-shower calorimeter (PCAL) are arriving, the extruded scintillator is being cut, and lead sheets and box parts are arriving, all in anticipation of starting assembly of the first PCAL sector in the coming spring. Stringing of the last sense wires is ongoing for the first sector of the region 2 drift chamber for CLAS12, and the second assembly line, at Old Dominion University, is now set up and ready to go. Thirty-eight (of 48) of the five-inch-diameter, quartz-face photomultiplier tubes have arrived for the high threshold Cerenkov counter and are being tested.
The Hall C Moller Polarimeter superconducting solenoid was cooled down, and the polarimeter was recomissioned, measuring beam polarization for the first time since the rebuild of the Hall C beamline. In addition, a paper based on Hall C experiment E02-019 has been published in Physical Review Letters: "Scaling of the F2 Structure Function in Nuclei and Quark Distributions at x>1."
PAC 37 Proposals Due Dec. 1
JSA Postdoctoral Research Prize Nominations Due Dec. 1
Outstanding Nuclear Physicist Award
The accelerator has been delivering beam to Halls A and C. Hall B finished its PrimEx-II run on Thursday. About two shifts were spent to optimize the machine optics. The 70 megahertz amplifier in the North Linac faulted twice, which affected the North Linac radiofrequency system. There is some noise (about 10 kilohertz) in the machine, causing double-pick in vertical beam positions, which can be seen in Halls A and C. The experts have been troubleshooting the problem.
The machine continued to perform well, allowing staff to continue FEL physics and detailed machine performance studies. The team also studied wiggler chamber heating under controlled conditions in preparation for future high power runs and performed radiation control measurements of the floor penetration in lab 1 to prepare for installation of the vacuum ultraviolet transport system.
Theoretical and Computational Physics
What is the velocity (or better, momentum) of a quark inside the proton? How does the motion of quarks depend on spin? Transverse momentum dependent parton distribution functions (TMDs) encode such information and relate it to asymmetries measured, for example, in semi-inclusive deep inelastic scattering. A new paper <arXiv:1011.1213> describes in detail a method to calculate TMDs using lattice QCD and discusses exploratory results obtained with a simplified operator geometry, building on lattice data components provided by the LHP and MILC collaborations.
Facilities Management and Logistics
Planning is underway for a power outage affecting all JLab campus buildings outside the accelerator site, excluding the VARC and ARC, for work on the campus electrical distribution system. The outage is currently scheduled to last for nearly the entire holiday shutdown period, beginning at 5 p.m. on Dec. 23 and ending at 6 p.m. on Jan. 2. There will be no power in these buildings during this period. More details will be announced as plans for the outage are finalized. If you have any immediate questions, contact Rusty Sprouse in FM&L, x7589.
JLab Calendar of Events
JLab's Safety Numbers
22 Days since Last Recordable Accident (JLab record: 331)
Environment, Health, Safety and Quality
Reminder: Golf Carts Must Use Headlights After Dusk
Leaves of Three, Let It Be
Beware Glowing Eyes in the Headlights
Today's Colloquium to Feature Graphene
Order Quark Cafe Desserts for Thanksgiving
JLab Children Invited to Winter Wonderland Party
JLab Jackets Available for Purchase