Jefferson Lab Weekly Briefs
November 9, 2011
12 GeV Upgrade
The Hall D Civil construction contractor is finishing with balancing the air and water for the mechanical systems and commissioning to verify all mechanical and electrical systems are functioning according to the design requirements. On Nov. 3, inspections were conducted by representatives from the Architect-Engineering firm, Facilities Management, future Facility Users and the ESH&Q Division to establish the contract punch list. Upon completion of commissioning and safety-related punch-list items, a beneficial occupancy inspection will be conducted to turn the Hall D facilities over from the construction contractor to JLab. The beneficial occupancy date is anticipated to be toward the end of November.
The week began with turning on the radiofrequency (RF) accelerating cavities and magnet power supplies and letting them run at low levels after being off for several months. During the day, Engineering Support staffers worked on their respective systems, while at night, Operations staffers locked up the accelerator and sent the beam around as far as possible. After wrestling with vacuum valves that did not want to open and RF cavities that did not want to stay on, beam was sent halfway around the accelerator to the first first-pass (1R) dump on Thursday morning. Just before midnight on Thursday, one full pass of beam was sent around to the second first-pass (2R) dump. Four hours later, another pass was added, taking beam to the 4R dump. Friday saw many punch-list items taken care of, after which rethreading the beam around was rather difficult. Beam optics was cleaned up, but then an as-yet-determined problem with a magnet at the end of the fifth arc prevented achieving a third pass through the machine. The two-pass beam was subsequently steered to the beam switchyard, and 25 microamps of continuous wave beam was delivered to the BSY dump. The new 12 GeV C100 RF cavities were then turned on and run at a modest 10 Megavolts per meter, with > 40 uA beam; they performed superbly. The machine was in the process of being set up for beam breakup testing when the Arc #1 power supply failed at 1 a.m. Monday, effectively halting any further work with beam in the accelerator. In addition, the temporary shield wall for the Hall D tunnel was installed, which will allow running beam in the main accelerator during Hall D construction.
A collaboration between theorists and experimentalists has revisited the question of "How well do we know the neutron structure function?" The new analysis of inclusive proton and deuteron deep-inelastic scattering data included realistic uncertainties in the nuclear corrections to the deuterium data, from which neutron information is extracted. The uncertainties arise from the deuteron wave function, nuclear smearing and nucleon off-shell corrections. The analysis provides an important baseline that will allow future, model-independent extractions of neutron structure, such as those planned at JLab following the 12 GeV Upgrade, to be used to examine nuclear medium effects in the deuteron.
The Machine Shop is presently manufacturing components for the first of three SPX cryomodule cavity assemblies. Additionally, the shop is also manufacturing CRM crab cavities for Argonne National Lab. Work also continues on building the accelerator injector's positron spectrometer vacuum chamber. The shop has processed 160 job requests since Sept. 26.
The Alignment group has been busy aligning detectors and components in Hall C in support of the Q-weak experiment. The Region 2 and 3 detectors, the quartz bar detectors and the target have been aligned. Additionally, alignment determined the amount of fill that is covering the new tunnel leading to Hall D.
JLab Calendar of Events
Nov. 16 Colloquium and Public Lecture
Environment, Safety, Health and Quality
Reminder: Golf Carts Must Use Headlights After Dusk
Beware Glowing Eyes in the Headlights
Computing and Networking Infrastructure
JLab Primary Nameserver Work Set for Tomorrow
Quark Cafe Offers Holiday Desserts
JLab Colloquium and Public Lecture Set for Nov. 16
Thanksgiving Warm-Up Buffet in the Quark Cafe
JLab 2012 Holiday Calendar Posted
Mobile Mammography Unit Onsite Dec. 7
Tracking Thomas at JLab
Congratulations this week go to Doug Higinbotham, Jason Willoughby, Russell Mammei, Michelle Shinn, Mike Wilson, Narciso Gomez, Christine Fragapane and Samika Hawkins, who were the first to correctly identify the Nov. 2 location. Honorable mentions go to Deborah Dowd, Harry Fanning, Sue Witherspoon, Ron Bartek, Jim Boyce, Karsten Flowers, Dick Owen and Stephanie Vermeire. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.