Jefferson Lab Weekly Briefs November 12, 2008
Jefferson Lab Weekly Briefs
November 12, 2008
12 GeV Upgrade
A Director’s Project Review (DPR) of the 12 GeV CEBAF Upgrade was convened at Jefferson Lab from Nov. 4-6. The primary focus of the DPR was to present the full project plan to a panel of 11 external reviewers and to discuss known issues facing the project (including staffing) as the construction phase begins. Members of the 12 GeV Upgrade Project Team made presentations to three subcommittees (Accelerator, Experimental Equipment and Management) for this review. A review committee report is expected in the near future.
After the successful completion of the commissioning of the polarized helium-3 target and of the BigBite detector system, experiments E06-010, Measurement of Single Target-Spin Asymmetry in Semi-Inclusive Pion-Electroproduction on a Transversely Polarized 3He Target, and E07-013, Target Normal Single-Spin Asymmetry in Inclusive DIS n(e,e') with a polarized 3He Target, have started taking production data.
Hall B is running the second phase of the e1-dvcs experiment. After initial startup problems of the machine and the equipment after a very long down time, the experiment is now running smoothly and is taking production data. The newly installed Moller shield allows to operate the tracking chambers at lower background rates.
The experimental halls received steady beam during this period, with a total of 220 hours of beam availability. A pass change to five-pass beam for all halls was accomplished midweek. The accelerator kept delivering beam to Halls A&B after Hall C experienced a schedule delay due to a magnet problem. Since then, a witness beam has been sent to the beam switchyard dump for orbit stability.
Free-Electron Laser (FEL)
FEL staff continued good progress on setup, producing nearly full energy and matched beam most of the way to the wiggler. The gun lifetime remains a limiting issue because of high background pressure. Staff members are making good progress in investigating the source of high pressure as they work around the limitations with frequent re-cesiations and also chase down a few stability issues with the radiofrequency and drive laser. The cathode will likely also be replaced during the next couple of weeks, and data are being taken to verify that need.
A fully relativistic and gauge invariant framework for calculating cross sections of dilepton production in nucleon-nucleon (NN) collisions has been developed (arXiv:0811.0739 [hep-ph]), which is based on the meson-exchange approximation for the NN scattering amplitudes. Production amplitudes include contributions from nucleon-nucleon bremsstrahlung as well as from the mechanism of excitation, propagation, and radiative decay of Δ(1232) and N*(1520) intermediate baryonic resonances. Δ isobar terms are found to dominate the cross sections in the beam energy range of 1-4 GeV.
JLab's Safety Numbers
63 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Nov. 18: Science Series Lecture: NextGen
Environment, Safety, Health & Quality
Over the years, Jefferson Lab's safety performance has dramatically improved. These graphs indicate a downward trend we should take great pride in and one to which we have all contributed.
During FY08, there were two recordable injuries, both of which resulted in medical restriction. Contrast this with 17 recordable injuries in FY01, nine of which resulted in medical restriction. The improvement is extraordinary.
FY05 was our turning point, when the predecessor of today's Safety Observation program was implemented. The elements of the program increased the efficacy of manager-worker communications, allowing for immediate feedback from both groups as well as data for improvement priorities.
Overall, JLab's injury rates have been driven down by many factors, but the consistent thread is effective communications. Whether it's feedback from a safety observation, closing a Corrective Action Tracking System (CATS) item, planning work with your team or sharing a lesson learned with your group, we all benefit from the results - and thus injuries are prevented.
Mobile Mammography Unit Onsite Dec. 8
Crane Operator and Master Rigger Training Scheduled
Science Series Lecture: Tuesday, Nov. 18
Colloquium and Public Lecture: Wednesday, Nov. 19
Holiday Desserts to Tempt Your Taste Buds