12 GeV Upgrade
At the Hall D construction site, the final portion of the new Accelerator site boundary fence is being installed. With the start of the CEBAF accelerator shutdown in mid-May, the contractor will remove the existing fence between the Accelerator site and the Hall D construction site, making Hall D part of the Accelerator site. This fence change will signal the start of excavation to the existing northeast stub of the accelerator tunnel for connection during the shutdown. The northeast portion of the accelerator ring road and the Hall D construction area will be posted as a construction work site with specific requirements for training and personal protective equipment (PPE). For safety reasons, access to these work sites will be limited to personnel involved with the civil construction project.
The Hall D construction contractor has transferred the last of the SEG shielding blocks and placed them in the electron beam dump. A number of concrete pours have taken place over the last few weeks, including the tagger area roof, the electron beam dump roof, the first sequence of the tagger truck ramp floor slab, the service building floor slab and the second lift of the service building south wall.
Hall A continued taking data for the x>2 experiment. The data taking on the deuteron and helium-4 was completed earlier. Last week, data were taken on helium-3, carbon, calcium-40 and calcium-48. Running was smooth and productive. Of the total eight kinematic settings, five settings were completed and one was mostly done. Data taking for the experiment is well on track to completion.
Research Assistantship Nominations Due May 31
Last week was another record-setting week for CEBAF accelerator operations. New records for peak injector current of 295 microamps and for the integrated charge in a 24-hour period of 17.98 Coulombs were established. Additionally, the beam availability was 82.4 percent for the week. The physics program for the week continues with the delivery of high-current beam to Halls A and C. Hall-B continues HDice target installation. Beam studies were performed Tuesday and Thursday. These studies included measuring the arc optics to document the present 6 GeV machine and in preparation for the 12 GeV machine. Beam studies time was also used to upgrade the bunch length optimization tool to be compatible with the new 130 keV gun/injector setup. On Thursday, the injector laser spot was moved to maintain high beam current, and the Wien was flipped from right to left for Q-weak. Over the weekend, an arc dipole box supply and a beam line vacuum valve malfunctioned, which interrupted beam delivery for a few hours. The faulty parts were replaced.
The FEL group established lasing at 2.15 microns for mirror testing and ran up to around 1 kilowatt in the initial setup. No signs of spurious mirror heating were observed at this level, and the group is in the process of optimizing the match so that higher efficiencies and powers can be produced.
Theoretical and Computational Physics
Members of the Theory Center, together with a collaborator at the University of Maryland, have computed the excited states of the nucleon and Δ within lattice QCD <arXiv:1104.5152>. They have, for the first time in a lattice calculation, determined the mass of baryons of high spin, up to 7/2, with many of the masses computed to high precision. The pattern of states observed is consistent with the non-relativistic quark model, but is inconsistent with and richer than the pattern of states observed in a quark-diquark model.
Facilities Management and Logistics
Now that Rattley Road is no longer closed after hours, it has been designated as the preferred route for all delivery vehicles. A new delivery route map has been posted to the JLab Construction Corner portlet on Insight. The map may also be accessed directly here.
Environment, Safety, Health and Quality
Use JLab Safety Knowledge to Protect Your Eyes
If you do injure your eye(s), always seek immediate medical attention. Here are some important first steps following a variety of common injuries that may help minimize the damage as you wait for treatment:
Worldwide Travel Caution Update
Information Session Offered on May 5 Reguarding Permits for Digging, Excavating or Making Floor/Wall Penetrations at JLab
Onsite TIAA-CREF Counseling Offered
Run-A-Round Is Set for May 11
Volunteers Needed for Run-A-Round
Radiation Worker Classes Scheduled
Tracking Thomas at JLab
Congratulations to Stephen Smith, who was the first person to correctly identify the April 27 location. Honorable mentions go out to Kelly Tremblay, Jim Follkie, Danny Machie and Will Oren. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.
JLab Calendar of Events
May 6-7: USQCD Collaboration Meeting