Jefferson Lab Weekly Briefs November 14, 2007
Jefferson Lab Weekly Briefs
November 14, 2007
In Hall A, the Coulomb Sum Rule experiment, E05-110, has been taking production data, but was interrupted this week for two days to warm up the heat exchanger in the warm helium return to the Central Helium Liquefier that had completely iced up. The production run is characterized by a multitude of short runs at different spectrometer momentum and angle settings and beam energies for a variety of targets.
The frozen spin target, FROST, has been installed in CLAS. The target is polarized at about 90 percent and is operating in the dilution mode and frozen spin mode. The polarization decay time has been estimated at about 3,500 hours at 35 milliKelvin (mK) temperature. The target has been ready for data taking since Monday night and is awaiting suitable beam for production data taking for experiment g9a, a search for new excited baryon states using polarized photons and polarized protons.
In Hall C, production data taking for GEp-III and GEp-2γ is proceeding with a measurement at Q2 of 5.2 (GeV/c)2 in progress.
This was a very good period for the accelerator, with more than 285 hours of beam delivery distributed among the three experimental halls. Procedures accomplished included an energy change. One short-lived problem was a failure of a fast valve controller card. It was replaced in the end of the North Linac. A longer-duration problem occurred when an End Station Refrigerator turbine bearing failed, bringing beam delivery to a halt while repairs are underway.
Free-Electron Laser (FEL)
President Bush signed a defense spending bill Tuesday that includes $2 million for the FEL. Safety approvals have been obtained for the 16-Tesla solenoid magnet test next week in the Terahertz lab. The radiofrequency systems were acid flushed. The Gun Test Stand gun tanks are now bolted together and ready to be pressure tested, and the safety enclosure for the GTS drive laser has been received. Preparations of the refurbished FEL gun continued, and the injector beamline is being prepared for a bake. A vexing problem was identified and fixed on the M55 accelerator diagnostic system. Lab 5 is now certified for local user operations.
Parity-violating electron-proton scattering is a technique that has been used at JLab to extract the strange form factors of the proton. To ensure that reliable information is obtained from the experiments, radiative corrections from two-photon exchange and photon-Z boson interference have been computed in arXiv:0711.0143 [nucl-th], which hitherto had not been accounted for in data analyses. Effects of order 2-3% were found at Q2< 0.1 GeV2, which are largest at backward angles, and have a strong Q2 dependence at low Q2.
JLab Children's Holiday Party
Quark Cafe Offers Thanksgiving Feast
Holiday Desserts to Tempt Your Taste Buds
JLab's Safety Numbers
JLab Calendar of Events
Nov. 22-23: Thanksgiving holidays
Environment, Safety, Health & Quality
It may not feel like it this week, but cold winter weather is just around the corner. Take some time this week to prevent damage to your home from your water pipes freezing and bursting. The Newport News Waterworks recommends the simple tips below to prevent major problems:
SLAC Pipe Explosion Lesson Learned
Computing and Networking Infrastructure
Dial-in Server Outage Planned
Scientific Computing Maintenance Planned
'Tis the season for E-Card Scams
Microsoft Office 2007 and Windows Vista
Redhat Enterprise Linux 5 Now Available
Windows Vista Deployment Information