Jefferson Lab Weekly Briefs March 23, 2011
Jefferson Lab Weekly Briefs
March 23, 2011
12 GeV Upgrade
Assembly of the first 12 GeV cryomodule continues. Assembly of the second cavity string has been completed; four cavities are ready for the third string. All beam transport quadrupole magnets have been approved for assembly into girders, including the QP magnet pairs to be used in arc 10; the girders with single QP magnets in arc 10 have been completed. The contract for the septum dipole magnets has been terminated and will be re-bid. The resultant schedule delay is not expected to impact installation milestones. The first high-voltage power supplies for the klystrons have arrived and been installed in zone SL24. The vendor for the warm compressor skids for the Central Helium Liquefier expansion has completed mounting the motors and compressors. All vacuum pump power supplies have been received. Feedthru-antenna assemblies for the beam position monitors are arriving.
Hall A techs fixed the quadrupole power supply on Tuesday; the 480-Volt power input had been wired with reversed phase, which because of how timing is derived from it effectively limited the efficiency and prevented full-power operation. Once this was fixed and the Q-weak target was cold, the short-range correlations experiment ran with its high-density target in production kinematics. Some timing problems were discovered and fixed on the BigBite spectrometer on Friday night. The experiment was in good data-taking mode until late Saturday night, when the accelerator could no longer deliver beam because of power supply problems. The rest of the weekend was spent trying to fix the accelerator, with no beam on target. As of Monday morning, these repairs were ongoing.
APS Award for Early Career Physicists
2012 APS Fellowship Submissions
Last week, the CEBAF accelerator delivered beam to both Halls A and C with 55.2 percent beam availability. Hall C reported that beam quality was much improved as a result of the optics work the previous week. Hall B was down for installation of the HDice experiment. On Tuesday, beam delivery was halted for 12 minutes for a tornado drill. On Saturday evening, the arc 2A box supply failed, which interrupted beam delivery. While the experts were troubleshooting the arc 2A box supply, the accelerator underwent beam studies and maintenance.
The FEL group successfully transported and measured the flux of vacuum ultraviolet photons in User Lab 1 and is setting up to measure the bandwidth of the output at ~10 electron-volts. Staffers operated the FEL accelerator for several shifts in support of irradiation experiments.
Computational and Theoretical Physics
The current constraints from lattice QCD on the existence of the H-dibaryon are discussed in a new brief report <arXiv:1103.2821>. The new work considers the constraints on the H-dibaryon imposed by simple chiral extrapolations of existing data. The extrapolation to the physical pion mass allows for either a bound H-dibaryon or a near-threshold scattering state, and further calculations are required to clarify this situation.
JLab Calendar of Events
March 28: Safety Shoe vendor onsite
Environment, Safety, Health and Quality
Keep children, pets safe from poisons
If you suspect your animal has been poisoned, call your veterinarian or the Animal Poison Control Center hotline at (888) 426-4435. Be prepared to tell the Center what the pet ate or drank and about how much. Source: PETA
Computing and Networking Infrastructure
MIS Applications Outage (Maximo/Requisitions/Work Requests)
Network Outage in CEBAF Center
Last Chance to Enter JLab 2011 T-shirt Contest
Don't Talk to Oprah Until You Call Public Affairs
Interested in Golf?
Sling a Softball with JLab Co-workers
In Need of Excess Furniture
Briefs Do Have a Style - and It's Changing!
Tracking Thomas at JLab
Congratulations to Stephanie Vermeire, who was the first person to identify the correct March 16 location. Honorable mentions go out to Rob Mahurin, Lori Zukerman, Tina Menefee, Jacqueline Bacon and Karl Slifer. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.