Jefferson Lab Weekly Briefs February 13, 2008
Jefferson Lab Weekly Briefs
February 13, 2008
12 GeV Upgrade
The draft specifications have been developed for the Hall B CLAS12 (CEBAF Large Acceptance Spectrometer ) Torus Magnet, one of the seven planned superconducting magnets associated with the 12 GeV Upgrade. A design and safety review of the Super High Momentum Spectrometer (SHMS) Hall C detectors was held at JLab on Jan. 22 with an emphasis on integration plans. Presentations were made by several Hall C Users, some of whom will construct detector elements through approved National Science Foundation Major Research Instrumentation grant funding. A successful technical design review of the continuing work on the Hall D Forward Drift Chambers was held at JLab on Feb. 1. Final reports from these review committees are expected this week.
Data taking in Hall C for E04-019, a measurement of two-photon exchange contributions in e-p elastic scattering using recoil polarization, was completed in late January. The BigBite magnet was then installed in front of the BigCal electron detector, effectively converting BigCal into a photon detector. Data taking was started for E07-002, a short run to measure polarization transfer in wide angle compton scattering. While this measurement got off to a good start, a leak in the Hall C beamline exit window stopped data taking before sufficient statistics were accumulated. With the support of the Radiation Control Group, the exit window was repaired. E07-002 was then able to run parasitically during a planned Hall B extension and obtained excellent statistics.
Halls B and C enjoyed 185 hours of beam delivery during this one-week reporting period. Hall B was the initial customer of the accelerator at the start of this week. After a vacuum problem was solved in Hall C, the hall started taking beam again on Feb. 6. The only equipment event was a North Linac Master Oscillator fault until the End Station Refrigerator (ESR) tripped on Feb. 10, which resulted in an 11-hour delay of beam delivery to the experimental halls. Once the ESR was back up, the accelerator performed well until it was shut down for the start of the Scheduled Accelerator Down (SAD) that started on Feb. 11.
Free-Electron Laser (FEL)
FEL staff continues the high-voltage processing of the Gun Test Stand gun and the FEL gun. Limits were encountered on both due to field emission from a bellows in the transmission line from the HV to the gun, so both pieces of hardware are being modified. In addition, the FEL optics group has completed the alignment and pumpdown of the entire Optical Transport System into all the user labs.
Deeply Virtual Compton Scattering (DVCS) with nucleon and nuclear targets is a key process to access Generalized Parton Distributions (GPDs), which provide three-dimensional images of quarks and gluons inside hadrons. In a recent paper, arXiv:0802.0669 [hep-ph], the generalized vector meson dominance (GVMD) model was used to describe DVCS from nucleons, and a good description of available DVCS cross section data was found over a wide range of kinematicals. DVCS from nuclear targets was also evaluated, and large nuclear shadowing effects were predicted.
JLab's Safety Numbers
147 Days since Last Recordable Accident (JLab record: 319)
Continuously Improving Safety at JLab
JLab Calendar of Events
Feb. 14: Valentine's Day (Quark Cafe special luncheon menu)
Environment, Safety, Health & Quality
Home falls are a major source of severe injuries and death for young children and senior citizens. For seniors, falls in or around the home are the most frequent accident. Some of the more dangerous home fall situations involve slippery floors, poor lighting, loose rugs, electrical cords in pathways and clutter. The following tips from the Centers for Disease Control and Prevention provide ways to minimize the risk of falls.
ORNL Lesson Learned on Assessing Work Control
Computing and Networking Infrastructure
New Windows Terminal Server Cluster Available
Employees Invited to Tour Lab
2008 Benefits Open Enrollment is Underway
Pollution Prevention Award Nominees Sought
JAG Dog Sports Training Club Informational Meeting
George Walker Retirement Farewell Reception set for Feb. 20