Jefferson Lab Weekly Briefs
September 3, 2008
12 GeV Upgrade
The CLAS12 detector is planned to operate at luminosities a factor of 10 higher than the present CLAS. Successfully operating at this design luminosity requires a high-magnetic (5 Tesla) solenoid field in combination with a carefully shaped shielding pipe with a conical outer profile and optimized detector locations. Extensive studies of the physics background rates were performed to finalize the design of the shielding geometry and the detector positions. These studies confirm the detectors can operate at the design luminosity of CLAS12.
The Request for Proposals for the CLAS12 torus magnet for Hall B has been sent out.
In Hall C, the installation of the Spin Asymmetries of the Nucleon Experiment (SANE) continues on schedule.
A leak was found on the radiofrequency waveguide vacuum window of SL09; the ceramic window had to be replaced. Load testing of all major magnet box supplies to 80 percent of rated capacity is nearly complete. Personnel Safety System (PSS) certification of RF and major magnet supplies has begun. Finally, a tour was hosted for Young-Kee Kim, the Deputy Director of Fermilab.
Free-Electron Laser (FEL)
The FEL is back under vacuum, and the gun bake is essentially complete, so FEL staff members were ready to begin preparations for operations following Labor Day. A HIPPO™ laser (a diode-pumped solid state Q-switched laser) from Spectra Physics was delivered for Lab 4. This laser is extremely compact, but puts out ~ 20 W (Watts) average at the fundamental wavelength of 1064 nm (nanometers), or up to nearly 7 W at 355 nm.
Corrections to polarized structure functions of the nucleon arising from finite values of the nucleon mass relative to the momentum transfer, Q2, have just been computed (arXiv:0808.2397 [hep-ph]) within a new theoretical framework (collinear factorization). These "target mass corrections" (TMCs) were found to be significant for the spin-dependent g1 structure function at large values of the Bjorken-x variable (the fractional momentum of the nucleon carried by quarks), but largely cancel in the polarization asymmetry A1 (the ratio of the g1 and spin-averaged F1 structure functions). A comparison of TMCs obtained from collinear factorization and from the "operator product expansion" formalism shows that at low Q2, the corrections drive the proton A1 asymmetry in opposite directions, which may have important consequences for the interpretation of low-Q2 structure function data at JLab.
The EESDCP (Electrical Engineering Systems, Direct Current Power) magnet power group, began system checkout of the magnet power supply system after extensive maintenance occurred during the summer down. All of the accelerator large magnet power supplies were brought online last week. Minor problems with a few were corrected immediately. Three supplies still need checkout, but all the others ran up to nearly the 6 GeV operating point. Further testing will occur in the coming days.
JLab's Safety Numbers
324 Days since Last Recordable Accident (JLab record: 324)
JLab Calendar of Events
Sept. 5: United Way School Tools Donation Drive ends
Environment, Safety, Health & Quality
Work continues on the four High-Performance Work Teams recently formed to address the findings of the HSS Review. Cross-functional teams were established in early August, with the intent of understanding both DOE and JLab requirements and then providing corrective action plans for each of the four HSS-identified areas. These areas include: Material Handling, Assessments, Issues Management and Event Investigation and Reporting.
There has been significant progress; each team has met multiple times, reviewing the issues, identifying root causes and providing corrective action structures that will not just meet DOE requirements, but will also improve JLab safety and performance over the long term. The teams will now finalize their corrective action plans. ESH&Q will then begin coordination of any work overlaps between teams. Finally, a synchronized plan will be provided to JLab management by mid-September. More information on the progress of these teams, as well as implementation of corrective actions, will be available in the coming months.
Computing and Networking Infrastructure (CNI)
Network Switch Upgrades in the ARC Building
During these maintenance times, the ARC network will be unavailable for several hours while the switches are upgraded to support automatic vlan assignment. To avoid extended outages after the upgrade, register your machine(s) now. If you have no network connectivity on the day following your scheduled upgrade, please contact the Computer Center HelpDesk at x7155. Upgrades for the switches on the other floors of the ARC building will be scheduled for a later date.
Maintenance Period Set for Sept. 16, 5-10 p.m.
JLab Welcome Picnic for New Director
All JLab staff and On-Site Users are invited to attend the event, which is sponsored by JSA, LLC. Come out and meet and welcome JLab's new director, Hugh Montgomery. The Quark Cafe is catering the picnic lunch, so the cafeteria won't be open for lunch that day. In case of inclement weather, the event will be moved indoors to CEBAF Center. An RSVP request has been distributed by e-mail.
CEBAF Center/VARC Parking Lot Closed Tuesday-Thursday, Sept. 9 thru Sept. 11
Tee'em Up for the JLab 2008 Fall Golf Tournament!