Jefferson Lab Weekly Briefs
March 16, 2011
12 GeV Upgrade
12 GeV activities for the upcoming six-month shutdown are fully integrated in the JLab sitewide schedule, and logistic planning is in full force. The goals for civil construction during this period include construction of the beam switchyard building addition with two new penetrations to the tunnel, connection of the existing tunnel to the Hall D tagger enclosure, and low-conductivity water upgrades. Upgrade activities for the accelerator include removal, refurbishment and reinstallation of all west arc dipole magnets and some east arc dipole magnets as well as the installation of the new four-meter magnets and girder assemblies in arc 10. In addition, three new C100 cryomodules will be installed in the south linac along with new radiofrequency zones and upgrades to the safety system. Two (potentially three) of the cryomodules will be commissioned.
Last week, Hall A switched from the N→Δ experiment to the short-range correlations experiment on Monday and made a target configuration change Tuesday and Wednesday. Meanwhile, several magnet repairs were underway. Unfortunately, the hall was down until Saturday because of the magnet power supplies, as techs struggled to repair them. As of Saturday, staffers found they could not run one of the magnets at full current and decided to run the rest of the weekend in a compromise configuration with that magnet at 85 percent current, which was good enough for some aims of the experiment. Presently, Hall A staffers are formulating a plan with electrical engineering support from the Accelerator Division to fix the faulty power supply, while the SRC experiment continues to run.
After replacement last week of the bellows near the Hall C beam dump, another leak was found, this time in the beamline exit window. The window was replaced, establishing an excellent vacuum. The Q-weak target was re-cooled and data taking was resumed, starting with event mode and background measurements, including an important "dilution" measurement, which establishes the correction required from the aluminum windows of the hydrogen target cell.
Research Assistantship Offered
Over the weekend, the CEBAF accelerator delivered beam to both Halls A and C. During the week, none of the halls were ready for beam: Hall A was changing to a different experiment and also worked on its left spectrometer Q1 magnet; Hall B was installing a new experiment; Hall C was working on its beamline vacuum and the QTor power supply. Accelerator staffers used the time to perform subsystem maintenance and beam studies. Beam studies performed included: improving beam quality for Q-weak, new injector optics, arc 1 rematch using the elegant decks and optimization of the accelerator optics.
The FEL team continued setup of ultraviolet generation in Lab 4 for the Laser Micro-Engineering Station. The team was successful in doubling the light frequency, but performance optimization continues. Staffers also installed the optical transport system to Lab 1 for vacuum UV and demonstrated operation of the vacuum monochrometer. Measurements of UV-driven thermal loading on the cavity mirrors was inconclusive due to issues with the measurement instrumentation.
The Mechanical Engineering Group has been gathering historical design data and drawings for the super-harp and the harp diagnostic devices. The g2P experiment requires super-harps to obtain measurements of the impacting beam angle at the target. Since there was no single design for the many configurations of the super-harp and the harp, the MEG design team sought to consolidate the two designs. The new design incorporates features from both devices so that only a few components are needed to produce either device. The design will be reviewed by various groups to ensure that it meets physics requirements. Fabrication will proceed shortly after.
Additionally, MEG's 12 GeV beam transport team has been focused on making final preparations for the May installation down. Presently, 26 of the 32 new arc 10 quadrupole girders have been assembled and are ready for installation. The arc 10 four-meter dipoles are making their way through the measurement process and will soon be outfitted with vacuum chambers and synchrotron radiation compensation coils. The magnet refurbishment bay double bridge crane has been installed, and the area is being organized to support arc dipole refurbishment.
Environment, Safety, Health and Quality
Applying JLab Work Safety Principles at Home
Computing and Networking Infrastructure
Windows Patch Delivery Set for Today
Maintenance Day Scheduled for Tuesday, 5-7 p.m.
Linux Patches Scheduled for Maintenance Day
Annual Property Validation Underway
Annual Key Validation Also Underway
JAG Seeks Design Entries for JLab 2011 T-shirt Contest
Tracking Thomas at JLab
JLab Calendar of Events
March 28: Safety Shoe vendor onsite