Jefferson Lab Weekly Briefs
July 27, 2011
12 GeV Upgrade
Thirty-six of the 48 barrel calorimeter modules for Hall D have now arrived at JLab from the University of Regina, Saskatchewan, Canada, with four more expected by the end of July. The first full layer of the forward drift chamber has been assembled (of 24 total needed), and is now being tested. The custom preamplifier ASIC, used for the forward and central drift chambers, has been produced via the MOSIS service at the University of Southern California and has been sent for packaging. All straws needed for the central drift chamber have arrived at Carnegie Mellon University, with 22 of the 28 barrel layers of straws inserted and wire-stringing done for four layers. The main production of 2500 (out of 3000 total) bases has been ordered by Indiana University for the lead-glass forward calorimeter.
In Hall B, the cryostat that will hold solid targets of polarized deuterium-hydride (HD) at the center of CLAS next November achieved its temperature goal of 0.05 Kelvin on July 22. The HDice group bubbled dilute 3He through super-fluid 4He to reach the low temperature, making it the first dilution refrigerator built to DOE’s new ASME code requirements. Solid HDice targets are polarized at even lower temperatures in the Test Lab and trucked to the experimental hall. Once loaded into the new in-beam cryostat for the coming g14 run, the spin can remain aligned for years. Using solid HD as a target provides unprecedented purity and will open a new window to the spectrum of the nucleon.
The injector experiment (PEPPo) continues with equipment checks in the injector. The new 5 MeV vacuum chamber's alignment check and leak check were both satisfactory. West arc magnet cooling water hose tightness and leak checks are ongoing. East arc magnet installation, alignment and hookups continue to go very well. Significant progress is being made in zone 2L24; at mid-week, the radiofrequency system was on at 1 kilowatt, and by the end of the week, RF was on to all eight klystrons at ~10 kW. As the power is ramped up, control system checks look good. Installation and circuit checks in 2L25 are coming along nicely, with six of eight klystrons installed at midweek.
FEL staffers prepared the gun for high-voltage conditioning and verified that the cathode protection mechanism was working. The group also installed the krypton gas system for processing. At the end of the week, the team started conditioning the gun under vacuum, reaching 220 kilovolts and noting that with the beamline still baking, and the pressure higher in the gun, the onset of gas desorption came sooner.
Center for Theoretical and Computational Physics
The I = 2 π π s-wave scattering phase-shift is computed in a new paper below the inelastic threshold using lattice QCD. These results are combined with chiral perturbation theory to extract the scattering phase-shift (and threshold parameters) at the physical pion mass. The analysis finds results that are consistent with determinations from the Roy equations and with the existing experimental phase shift data.
The installation team is continuing work on the beamline components in the east arc's south quadrant. The low-conductivity water hoses are also being installed at this time. The LCW tightness checks have been ongoing in the west arc's south quadrant. In Hall A, the FZ1 dipole for the G2P experiment was installed. Additionally, the FZ2 stand was installed and grouted. The vacuum group continues to perform hook-up and routine maintenance throughout the entire machine.
Environment, Safety, Health and Quality
Pedestrians Reminded to Use Sidewalks at JLab
The ESH&Q Division reminds everybody at JLab to use the sidewalks, crosswalks and marked foot paths when walking on JLab property. With the volume of traffic on our roads and in our parking lots and the variety of vehicles, it is important to separate pedestrians and vehicles. Walking through parking lots and on roads can expose pedestrians to unnecessary risk. Recently, new walking path signs were added between the VARC and CEBAF Center to help remind people to use the sidewalk running down the east side of the parking lot. In addition, a new crosswalk was painted to connect the ARC and Building 19 sidewalk with the sidewalk running between the VARC and CEBAF Center. If you become aware of an area where a crosswalk or marked foot path could improve pedestrian safety, contact Tina Menefee. Here are some additional safety tips for pedestrians and drivers onsite:
Mont on the Six Month Shutdown
Six Month Shutdown Safety Briefing
Stockroom Adds Tools to In-Stock Catalog
Department of Energy Sponsors Food Drive Through Aug. 5
JLab Community Invited to Summer Interns Poster Session
Engineering Announces Special Cryo Seminars
JLab Property Passes Now Available Online
Tracking Thomas at JLab
Congratulations to Dave Fazenbaker, who was the first person to correctly identify the July 20 location. Honorable mentions go to Jason Willoughby, Michael Spata, Whit Seay, David Abbott, Randy Michaud, Kelly Mahoney, Andy Kowalski, Eric Forman, Doug Higinbotham, Lori Zukerman and Harry Fanning. Check out the Tracking Thomas webpage for a better view of his last location and this week's new mystery photo.
JLab Calendar of Events
July 29: Summer Intern Programs Poster Session, CEBAF Center lobby