12 GeV Upgrade
The pre-construction meeting for the beam switchyard addition contract was held on March 28 and included initial discussions on installation details for the new tunnel penetrations. The cooling towers for the North and South Access low-conductivity water upgrades have been set on the structural steel framing. The Hall D construction contractor is finishing the formwork for the 3-foot-thick concrete roof on the Tagger Area. The concrete pour, totaling approximately 700 cubic yards, is anticipated the week of April 11.
Hall A has been in a smooth production mode this week for the short-range correlations experiment, except for one problem that caused a loss of a day. During a spectrometer move, some cables snagged on the power cord of a vacuum pump for one of the quads on the spectrometer, causing the insulating vacuum to degrade. Future spectrometer moves during this running period will be coordinated by qualified techs with inspection of the area to verify no obstructions. However, apart from this problem, the experiment efficiency has been very high and the data looks good.
Hall B has completed a re-commissioning run for the photon tagging system. Scintillator counters of the photon tagger were removed before the Two Photon Exchange experiment to prevent exposure to high radiation during that run. The tagger focal plane detectors (over four hundred scintillators) were reinstalled after the TPE run was completed and a calibration run with CLAS and a liquid hydrogen target took place March 25-31. The goals of the calibration run were to verify the working order of the counters and collect enough data in exclusive channels to be able to check energy calibration (focal plane alignment) of the tagger. The Hall B tagger and the CLAS detector performed well during the run. Some broken counters were identified and will be repaired. A total of 1 billion triggers were collected with a single- and two-charged-track triggers to check energy calibration of the tagger. The Hall B tagger is ready for the upcoming G14-HD experiment.
Hall C was down until last week while a gasket was replaced on a leaking bellows flange near the dump. Water cooling was added to the bellows, which showed signs of heating from the beam. In addition, the bellows was instrumented with several temperature sensors to monitor beam heating effects. Since these repairs, Q-weak has returned to production data taking at currents up to 160 microamps with high efficiency.
Last week, the CEBAF accelerator delivered beam to all three halls with 92.5 percent beam availability. The highest combined current out of the injector was 190 microamps. Hall A was off for several hours due to a configuration change. The Hall C vacuum issue was resolved by Tuesday, and the hall started to take high current beam. After finishing its tagger calibration Thursday morning, Hall B stayed offline for HDice installation. On Sunday, the laser spot was moved to maintain high current for Q-weak.
The FEL team switched the system back to infrared operations and successfully lased at 1 micron and provided continuous wave electron beam in preparation for mirror and Terahertz tests in the coming week. The team also had a significant presence at the 2011 Particle Accelerator Conference in New York, with several papers and posters.
The Survey and Alignment (Metrology) group has measured and run quality control checks on the space frame and end cans for the next C-100 cryomodule. Metrology also fiducialized an R-100 cryomodule, the 12 GeV QP magnets and the Hall A g2p septum magnet. Fiducialization is a process that relates a component's mechanical and/or magnetic center to targets on the exterior. These targets are then used to position the component in the ideal beam location in the accelerator or end stations. The magnet measurement group continued to measure and qualify the XP family of 4 meter dipoles that will be installed in pass 10 of the west arc. Twenty of the 37 XPs have been measured so far. No problems have been identified.
Environment, Safety, Health and Quality
Safety Reminder from Radiation Control
Spring Yardwork without the Headaches
CCPR from Anywhere
Free Stock Has Furniture and Materials Available
Refresher Session: Getting Your Paper Approved for Publication
An App in Every iPot
Tracking Thomas at JLab
Congratulations to Jason Willoughby, who was the first person to correctly identify the March 30 location. Honorable mentions go out to Mike Martin and Elaine Zuchowitz. 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
April 8-9: QCD Evolution Workshop