12 GeV Upgrade
Twenty-eight of the 48 barrel calorimeter (BCAL) modules for Hall D have arrived at JLab from the University of Regina, Saskatchewan, with four more expected in early May. Following a successful construction readiness review, assembly of the forward drift chamber cathode and wire planes is underway. The custom preamplifier ASIC, used for the forward and central drift chambers, has been ordered via the MOSIS service at the University of Southern California. First shipments of the lead-glass blocks have arrived from Indiana University for the forward calorimeter for Hall D.
Last week, Hall A took beam for the x > 2 experiment, except for the target change, which required three days, as planned. Over the weekend, x > 2 ran smoothly, making good progress on its run plan. On Saturday morning, there were some instabilities in the accelerator, which were fixed by the afternoon. Otherwise, beam delivery has been great.
In Hall C, the Q-weak experiment completed data taking for an auxiliary measurement of the asymmetry of the electro-induced proton to Delta transition. Production data taking continued with elastic scattering on liquid hydrogen.
Research Assistantship Nominations Due May 31
JSA Promising Young Scientist Program
Last week, 278 microamps of combined beam current was delivered to Halls A and C, resulting in a CEBAF accelerator record for the integrated charge of 17.1 Coulombs extracted from the cathode in a 24-hour period. The beam availability was 74.2 percent. On Wednesday, the Central Helium Liquefier tripped due to 2K cold box oscillations. The cause of the oscillations has been under investigation. On Saturday, high-current beam delivery was interrupted due to machine instability. Experts quickly identified the cause and resolved the issue; beam delivery was resumed without problems.
The FEL performed a temperature bump in the injector cryounit to drive off helium. This will permit high-current running tests at 2 microns planned for the coming weeks. The FEL team also installed the required 2.2 micron optics and began setting up the machine for this effort.
Theoretical and Computational Physics
In a recent paper <arXiv:1104.4101>, the volume dependence of the octet baryon masses and relations among them were explored with lattice QCD. A comparison of the volume dependence with the predictions of heavy baryon chiral perturbation theory was performed in both the two- and three-flavor expansions, and predictions of the three-flavor expansion for the hadron masses were found to describe the observed volume dependences reasonably well.
Mechanical Engineering reports preparations are continuing for the six-month down. The existing dipoles in both the east and west arcs need to be removed from the tunnel, brought to the surface to the magnet measurement test facility (General Purpose Building #36), refurbished and then re-installed back into the exact positions they were in prior to removal. Currently, the group is conducting refurbishment practice, manufacturing of fixturing and documentation efforts.
Additionally, the magnetic measurement of all the XP-style magnets has concluded, with vacuum chambers, magnet pairing and magnet locations now assigned. Synchrotron radiation coils for the XPs are being manufactured and installed, along with vacuum chambers. All of the Arc 10 quadruples have been mounted on girder assemblies and have been moved to storage pending installation.
Part of the refurbishment efforts include installing an H-steel return leg, which is needed to reduce the field saturation caused by the higher energies running at 12 GeV. The H-steel required for the west arc during the six-month down has arrived, and shipments of H-steel required for the remainder continue to arrive weekly.
Several new families of dipole magnets have arrived for the spreader/recombiner/extraction regions of the accelerator. The septa contract was awarded to a new vendor and all of the material has been transferred and inventoried to begin manufacturing.
Environment, Safety, Health and Quality
Inspecting Safety Equipment
Take a few seconds to inspect any personal protective equipment before use; your well being could depend upon it.
Check Training for Shutdown Activities
Pressure Systems Fundamentals Class Offered
Annual Property Validation Ends This Week
Annual Key Validation Ends This Week
Onsite TIAA-CREF Counseling Offered
Run-A-Round Is Set for May 11
Radiation Worker Classes Scheduled
Tracking Thomas at JLab
Congratulations to David Fazenbaker, Jason Willoughby and Stephanie Vermeire, who were the first people to correctly identify the April 20 location. Honorable mentions go out to Percy Harrell, Brian Kross, Will Oren, Mary Beth Stewart, Greg Adams, Narciso Gomez, Dick Owen, Russell Mammel, Casey Heck, Lori Zukerman, Calvin Mealer, Jim Follkie, Mike Martin, Brita Hampton, Stephen Smith, Susan Brown, Greg Marble, Johnie Banks, Tonya Evans, Evelyn Akers, Doug Higinbotham and Dena Polyhronakis. 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
May 3-4: CEBAF Pre-Shutdown Safety Meetings (All Staff)