Jefferson Lab Weekly Briefs
October 20, 2010

12 GeV Upgrade

The fourth group of four barrel calorimeter (BCAL) modules for Hall D has arrived at JLab from the University of Regina, Saskatchewan, Canada, meaning one-third of all the modules are on-site. The first units of the new Cockcroft-Walton type high-voltage synthesizer-and-divider bases for the Hall D forward calorimeter passed acceptance tests at Indiana University, thus 500 of the total 2800 have been ordered to start mass production. Tests of first-article preamplifiers for the central and forward drift chambers, using the custom application-specific integrated circuit developed in collaboration with the University of Pennsylvania, were completed successfully. Therefore, all key elements of the electronics chain for the Hall D tracking detectors are now entering mass production. Manufacture of the custom 16-channel 250 Megahertz flash analog-to-digital converter, key to calorimeter, time-of-flight array and tagger hodoscope readout, has also begun, with assembly of the first 20 production boards. The largest of the Hall D solenoid magnet coils has been installed in the Test Lab stand and is being prepared for cool-down and full-field tests later this fall.

Physics

Hall A continues commissioning E07-007 and E08-025 (deeply virtual Compton scattering).

Commissioning of Q-weak and the Compton polarimeter continues in Hall C. No significant boiling of the liquid hydrogen target is seen up to 150 microamps. Initial studies of the sensitivity of the detectors to beam motion are encouraging.

Accelerator

The accelerator has been delivering beam to all three halls, with some downtime. Monday was a scheduled maintenance day for reactivating the injector photocathode and reconfiguring the low-conductivity water for the end stations. Over the weekend, some misbehaving radiofrequency cavities caused a couple of hours of downtime. Last week, beam energy was slightly off after the Arc2 box supply was replaced. The problem was corrected in a timely manner. After gun high-voltage power cycling, sometimes the injector orbits do not reproduce. The experts are still investigating the problem, and a work-around method has been implemented.

Free-Electron Laser

The FEL team continued gain-scaling measurements last week, while operating at both the 400-nanometer region and 700 nanometers. The small signal gain appears to be significantly over 100 percent, and lasing is easily established each day. A power meter had to be replaced due to damage from the optical beam. The team also managed to find the source of an annoying phase jump in the injector system in an over-torqued splitter connection to a radiofrequency module.

Center for Theoretical and Computational Physics

Quarks, the building blocks of protons and pions, carry a property we call color that comes in three shades. However, theorists like to imagine how the world changes as the number of colors increases. This provides a way of telling the difference between mesons that are thought to be made of a quark and an antiquark and those that might have more complicated configurations. The lightest meson that is unstable under the strong interaction, the σ (sigma), a meson that is important in nuclear forces, is thought to be such a more complicated state. A recent study by JLab's Michael Pennington and collaborators <arXiv:1009.6204> provides evidence that in a world with a larger number of colors than three, the σ would be a quark-antiquark meson, just like most of the other mesons we know of. They then explain how the σ changes its nature as the variety of shades is reduced to its physical number three, while ensuring a property known as "semi-local duality" holds, whatever the number of colors.

Environment, Safety, Health & Quality

Halloween is a fun time for kids, but it is also an important time to be extra vigilant for possible safety hazards so that your children have a fun and safe holiday. Click the link for timely tips from the U.S. Product Safety Commission to keep your little trick-or-treaters out of harm's way.

Computing and Networking Infrastructure

Microsoft Patches Will Be Released Tuesday
Microsoft released several critical patches last week for Windows systems. Due to the nature of these patches, the CNI group has decided to send them out to all Computer Center-managed Windows machines, starting on Tuesday, Oct. 26. If your desktop is managed by the Computer Center, please log out at the end of your workday next Tuesday, but leave your system powered on so that the patches can be installed during the night. If you experience difficulties with your computer in the morning, first reboot to see if that fixes the problem before contacting the IT Division Helpdesk at x7155 for assistance.

Introduction to Mailman for List Owners/Administrators
If you are the list owner or administrator of a mailman mailing list, this informative seminar is for you. The seminar will cover important mailing list topics, such as: how to start a mailing list, where to find the directory of mailing lists provided by JLab, how to get information concerning a mailing list (including its owner), and where to find help in administering a mailing list. The seminar will be held in the CEBAF Center auditorium on Monday, Nov. 1, 1:30-2:30 p.m. Plan to attend if you are currently the list owner or administrator of a JLab mailing list, or if you are planning on requesting a new mailing list for use at JLab. For more information, contact the IT Division Helpdesk at x7155.

Discontinuation of Dial-up Modem Pool (RAS) Service
On Nov. 1,  the lab's dial up modem pool (RAS) service will be decommissioned. The service, once widely used for off-site access, has been effectively replaced by the Internet. Questions about remote access to lab resources can be directed to the IT Division Helpdesk, x7155.

Announcements

Sentara Mobile Mammography Unit Onsite Dec. 6
The Sentara Mobile Mammography Unit will be at JLab on Monday, Dec. 6, 9 a.m.-3 p.m. in the ARC parking lot. This service is open to all employees as well as family members or friends, since personal health insurances will be billed. The procedure takes 15 minutes. To make an appointment, call 1-800-SENTARA (736-8272) or see the Screenings and Events section on the frontpage of the Sentara website.

Win an iPad in United Way Raffle
Raffle tickets for two 16 gigabyte iPads are $1 each and may be purchased at a table in the CEBAF Center lobby, 12-1 p.m., on workdays through Oct. 27. A winning ticket for each iPad will be drawn during the Jefferson Activities Group's Oktoberfest on Wednesday, Oct. 27. Winners need not be present to win and will have until Monday, Nov. 1 to claim their iPads.

JLab Calendar of Events

Oct. 22: Safety Shoe vendor onsite
Oct. 27: JAG Oktoberfest
Oct. 28-29: Transverse Spin Phenomena and Their Impact on QCD Workshop
Nov. 4: Safety Shoe vendor onsite
Nov. 23: Science Series Public Lecture
Nov. 25-26 Thanksgiving Holiday - JLab closed

JLab's Safety Numbers

51 Days since Last Recordable Accident (JLab record: 331)
51 Days since Last Lost Workday Accident (JLab record: 676)