Jefferson Lab Weekly Briefs August 18, 2010
Jefferson Lab Weekly Briefs
August 18, 2010
12 GeV Upgrade
There is a great deal of 12 GeV civil construction activity in progress. In the accelerator tunnel, installation of the low-conductivity water (LCW) header pipe for the 10th arc commenced with the start of the summer Scheduled Accelerator Down. At the North and South Access Building additions, the sitework is being completed with asphalt paving. At the Central Helium Liquefier (CHL) building addition, the underground portion of cooling water piping for the CHL #2 compressors is being installed from the cooling towers to the west end of the new addition. Also, SEG blocks for the Hall D photon beam dump and electron beam dump are being transported to the Hall D construction site. The concrete roof for the Hall D truck ramp has been placed.
Hall B has successfully completed a major data-taking run: g9b. A total of 15 billion events were collected using the excellently performing polarized frozen spin target, "FROST." This marks a huge milestone of the N* program with CLAS: For the first time, data collection for several "complete experiments" has been finished. It requires the measurement of meson production with unpolarized, circular and linearly polarized photons, as well as transverse and longitudinally polarized targets, and the measurement of recoil polarization of baryons. As a minimum, eight independent measurements are needed. CLAS has obtained 16 measurements for some channels. The combination of previous run groups and the current run group has finally achieved this goal. "Complete measurements" allow the experimenters to determine the production amplitudes for pseudoscalar meson photoproduction in a truly model-independent way, the Holy Grail of N* physics for the past 35 years, when the corresponding theory paper by Barker, Donnachie, and Storrow appeared in Nucl. Phys. B95, 1975.
Operations began the week delivering beam to the halls. On Thursday, the injector was commissioned with higher gun voltage. The commissioning went well, with gun2 voltage raised from 100 to 130 kilovolts. The higher voltage will make high-current beam transport better. Hall C received beam with gun2 at 130 kV. At 7 a.m. on Friday, the spring run ended successfully and the Scheduled Accelerator Down started.
Last week's efforts were focused on installation of the final components required for turn-on of the ultraviolet FEL. After considerable exemplary effort by many FEL staff members, the final required hardware components (wiggler chamber, the optical cavity mirror metrology system, viewers, beam position monitors, optical diagnostics and controls) are in place and pumped down. The rapid progress and successful completion of this work is another indication of the dedication and enthusiasm of all involved.
JLab's Safety Numbers
33 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Computing and Networking Infrastructure
CNI Systems Maintenance: Aug. 24, 5-10 p.m.
Shutdown of wireless network 'jlab_secure' on Aug. 24
Redhat Enterprise Linux Version 3 Support Ending
Lost and Found Online
Onsite TIAA-CREF Counseling Offered
Construction & Maintenance Recyclables Are Hot Commodities
JLab Strategic Plan Available Online
American Red Cross Blood Drive Results
United Way School Tools Drive Underway