Jefferson Lab Weekly Briefs
May 20, 2015
12 GeV UpgradeHall C: Connection of the Hall C SHMS Horizontal Bend (HB) magnet to all of its services was completed and the magnet was successfully cooled-down to liquid-helium temperature (4.2K). A challenging aspect of this magnet is that the distance between helium-temperature and room-temperature pieces is only a few millimeters in some places. The successful cool-down shows that this challenge has been met. During initial tests, the magnet was operated successfully at 10 percent of its eventual operating current. Careful engineering studies are being performed in preparation for full-current testing. The vendor building the Q2, Q3, and Dipole magnets is half-way through a series of practice tests that will conclude with shrinking the large metal collars onto the dipole magnet coils.
The new support system for the massive steel yoke of the SHMS Q2 magnet has been installed, and progress has been made towards completion of the gas system of the Heavy Gas Cerenkov detector. Installation of the large number of signal and high-voltage cables for all of the SHMS detectors continues.
Hall B: The Heavy Photon Search (HPS) Experiment in Hall B completed its Engineering Run on May 18, the last day of the extended Spring CEBAF running schedule. Working nights and weekends while CLAS12 construction proceeded during the week days, HPS was able to complete detector installation and fully commission its beamline, electromagnetic calorimeter, trigger, data acquisition system, and silicon tracker. Beginning in early May, HPS took its first physics data, including 1/3 of a PAC week in its design configuration, where its silicon microstrip detectors are a mere 500 um above and below the beam. Thanks to the tiny, stable CEBAF beams and lack of beam halo, this worked perfectly. HPS is searching for signs of a massive cousin to the photon which decays to electron/positron pairs and may couple to the dark matter.
Published Journal Articles, May 11-15, 2015
Kondo Gnanvo, et. al. "Large size GEM for Super Bigbite Spectrometer (SBS) polarimeter for Hall A 12 GeV program at JLab." Nucl.Instrum.Meth.A 782, 71-86 (2015).
K. Chirapatpimol et al. (Hall A Collaboration). "A precision measurement of the p(e,e'p)π0 reaction at threshold." Phys. Rev. Lett. 114, 192503 (2015)
Nicholas Zachariou, et. al (CLAS Collaboration). "Determination of the Beam-Spin Asymmetry of Deuteron Photodisintegration in the Energy Region Eγ=1.1-2.3 GeV." Phys. Rev. C 91, 055202 (2015).
Center for Theoretical and Computational Physics
The spin-dependent cross sections for semi-inclusive lepton-nucleon scattering have been derived within the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite momentum transfer. At leading order in strong coupling, the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. The size of the hadron mass corrections is estimated at kinematics relevant for future semi-inclusive deep-inelastic scattering experiments at Jefferson Lab.
The Electrical Engineering Systems (EES) department has been busy the last couple weeks supporting the end of the Accelerator beam operations and preparing for the start of the summer shutdown. The shutdown began Monday, May 18. The major activities in the coming weeks will be preventive maintenance work on RF systems, magnet power and instrumentation and controls hardware. Safety system recertification will follow maintenance and upgrades on the personnel safety system. Other major tasks include:
Environment, Safety, Health and Quality
Personal Protective Equipment (PPE): The last mitigation to an electrical hazard
AnnouncementsFestival Volunteers Needed Saturday, May 30, and Sunday, May 31, Jefferson Lab Public Affairs requests your help staffing its outreach tent at the Hampton Blackbeard Pirate Festival. Through the new festival program, we hope to spread awareness in Hampton Roads about JLab's work and its role in the national lab system. You'll help by assisting with children's activities, talking about the lab and handing out information. On each of the two days, Public Affairs will need volunteer help in four-hour blocks: from 10 a.m. to 2 p.m., and from 2 p.m. to 6 p.m. If you can join us, please e-mail Mike Robbins at firstname.lastname@example.org or call x7617.
Lab-wide Annual Property Inventory Will Take Place June 1 – July 31
Travelers and Travel Coordinators: Remember Expense Report Deadlines
JLab Implements Process to Improve Public Access to Research Results
Jefferson Lab Calendar of Events
|JLab Weekly Briefs is an ongoing publication providing information on the status of safety, accelerator operations, experiments, free-electron laser, reviews, upcoming activities and special events. Deadline for submission is every Tuesday by 10 a.m. Submit new items to: Public Affairs or contact Kandice Carter at x7263.|