May 20, 2009
12 GeV Upgrade
Detailed physics simulations for the CLAS12 detector in Hall B suggest that a change in the diameter of the inner warm bore of the torus magnet will improve operation of CLAS12 wire chambers at full-design luminosities. The impact of this bore change on mechanical dimensions, integrated field values and stress analysis was studied and found to be small. A Change Request describing this design change was submitted to the 12 GeV Change Control Board and was approved.
Hall D recently held a three-day collaboration meeting at JLab, mainly dedicated to updates on various subsystems, while Hall B held a meeting with foreign collaborators on vertex tracking systems in the CLAS12 central detector.
In Hall A, production running for experiment E05-102, Measuring the Transverse Asymmetries in the 3He(e,e'd) Reaction, has been proceeding very smoothly.
Hall B is currently carrying out the second part of two highly rated experiments on generalized parton distributions and transverse-momentum dependent parton distributions. After an initial one-week delay due to an incident that damaged a vital component of the polarized target, the run has been going well, and some of the lost time has been made up by excellent performance of the accelerator and the polarized target. Target polarizations in the range of 75-85 percent have been achieved. The experiments also make use of the lead-tungstate crystal calorimeter to detect high-energy photons at very forward angles. So far, the calorimeter has been performing flawlessly.
The accelerator was running well, with some isolated incidents. Monday morning, May 11, there was a power loss in the east arc due to a local breaker trip. That evening, the east arc box supplies tripped off twice, most likely due to power surges. Several hours were spent for beam studies. On Saturday evening, a west arc vacuum valve closed due to a cracked air hose, and the faulty hose was replaced. Sunday morning, two vacuum valves in the South Linac closed due to deteriorated high-voltage cabling. The valves were opened and the faulty cable will be replaced during the summer down.
Free-Electron Laser (FEL)
Taking advantage of the FEL's continued down for the low-conductivity water line installation, the team has made good progress on the ultraviolet line. This week, staffers activated the beam viewers, which use the first control system implemented with PC/104 and the required infrastructure. In addition to this, staffers also did work on the gun, drive laser, optical transport system and mechanical systems for the new gun and the UV beamline.
A new technique has been developed <arXiv:0905.2160 [hep-lat]> for constructing quark operators in lattice QCD, which allow efficient calculation of a broad range of hadron correlation functions. The method yields promising signals for meson, baryon and multi-meson systems on realistic lattice sizes with light dynamical quarks. The techniques outlined in this paper will be used in a range of spectroscopy determinations to support the JLab experimental physics program.
JLab's Safety Numbers
135 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
May 20: JLab Annual Run-A-Round
Summer Education Calendar
Environment, Safety, Health & Quality
According to 2007 U.S. Bureau of Labor Statistics data, falls down stairs or steps, falls from floor, dock or ground level and falls on the same level accounted for 19 percent of falls that resulted in fatalities. BLS data from 2006 showed that floors, walkways and ground surfaces were the source of injury and illness for 18 percent of all days-away-from-work cases. Also in 2006, slip, trip and loss-of-balance injuries without falls led to 35,440 non-fatal injuries.
Although worker injuries and fatalities due to slips, trips and falls have increased over the last five years, the good news is that they are highly preventable. Contributing factors, such as flooring type and condition, workplace environment, footwear and human behavior, can be readily addressed with the right tools in place. In fact, studies have shown that workplace slip, trip and fall prevention programs can significantly improve workplace injury rates over time. These programs identify hazards long before they have the potential to turn into serious incidents, and the programs help workers better recognize and report hazardous conditions in the workplace.
JLab's last reported slip, trip and fall incident occurred last August. Various preventive measures have been implemented to prevent further occurrences, such as the evaluation of all site entrances and exits for non-skid application, use of the safety paths between the ARC and CEBAF Center, and heightened communications regarding slip, trip and fall safety. Given the wet conditions of the season, all lab personnel should remain aware of these hazards.
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Last Chance to Enter the APS Toy Box Physics Contest
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