Jefferson Lab Weekly Briefs
April 25, 2012
12 GeV Upgrade
The cryomodule voltage needed for delivering 12 GeV beam to Hall D is 98 Megavolts. This performance was demonstrated during a recent beam study period, when a C100 cryomodule was successfully operated at 98 MV for one hour. Both in-tunnel C100 cryomodules are now operating with piezo-electric tuner resonance control, resulting in substantial improvement in detuning. Installation of the compressors and 4.5 Kelvin coldbox for the Central Helium Liquefier - 2 continues. Procurement actions are underway for the box power supplies for the arc dipole magnets. Field measurements of the new curved dipole magnets for the beam transport spreaders and recombiners have been completed. The magnets met all specifications, including close approximation of the predicted shunt settings. Fabrication of the new stripline beam-position monitor cans continues.
In Hall A, the g2p / GEp experiments have been running smoothly this week, finishing several kinematic points. If the hall keeps running like this until May 18, it will be a nice success.
Hall C completed running with the 877 MeV beam. Using the Q-weak apparatus, the parity-violating asymmetry of the nucleon to delta transition was measured to a precision better than one part per million. In addition, non-parity-violating asymmetries with transversely polarized beam were measured for the nucleon to delta transition and for Moller (electron-electron) scattering. Q-weak is now measuring the asymmetry of inclusive scattering of 3.35 GeV electrons on hydrogen. This measurement will constrain the uncertainty on one of the largest corrections to the measurement of Q-weak.
Voting in Users Group Elections Open Through April 30
The accelerator completed its low-energy run. The C100 radiofrequency zones ran at relatively lower levels, while preparations were made to push for higher gradients, which was planned for Thursday. On Thursday, a mini-scheduled accelerator down/beam studies day was taken in preparation to return to high energy. Preparations were also made to support high beam loading for the C100 zones. The injector experiment, PEPPo, tests were carried out in parallel with RF recovery and work on C100 zone 2L25. During the workday, tours for the NASA pressure vessel group and Beam Instrumentation Workshop were conducted. The accelerator energy was increased and all halls were reconfigured to new passes. The configuration change continued through Friday, with all halls taking low current until Saturday. During the weekend, the accelerator was configured for high current Hall C running. Operations staffers delivered 150 microamp beam to Hall C at 3-pass, with C100 zones set at 70 MeV each. Beam was terminated to Hall B on Sunday for planned work on the HDice target.
The FEL continued to run well for 16 hours a day, with day shifts for 2.2 micron mirror tests and wall plug efficiency studies, and evening shifts for terahertz users and Darklight experiment background measurements.
The Mechanical Systems Installation group recently completed many tunnel low-conductivity water leak repairs in a single day, resulting in an 85 percent reduction of LCW loss. Other LCW work supporting the 12 GeV Upgrade has been started, including the tagger dump skid installation and the beam switchyard service building LCW header upgrade.
A new 12 GeV floor-to-ceiling stand was temporarily installed at the tagger dump to Hall D, allowing for the validation of new tooling for the stand. Additionally, the ceiling stand was used by the Survey and Alignment group to train new staff on stand alignment. A ceiling plate test fixture, a ceiling plate install lift and an overhead ceiling plate drill press were added in support of the upcoming 12 GeV down.
The vacuum group has also made a lot of progress to support the upcoming 12 GeV down:
Environment, Safety, Health and Quality
When planning work at JLab, each group should always have some type of plan for what will occur. Some of these plans are formal written documents, with a completed Task Hazard Analysis (THA). During this work, there may be short, quick jobs that may not have been covered in the THA or rise to the level of hazard requiring a THA. A simple review, called the SAFE Plan, can help avoid hazards and serious potentials. The SAFE Plan is:
Computing and Networking Infrastructure
Email Migrations into New System Ongoing
Education Seeks Projects for Summer Honors Interns
Colloquium: From Quarks to Baseballs - The Evolution of a Physicist
RadCon Seminar: Anticipating Radiation Damage: Calculation of Relevant Quantities
Tracking Thomas at JLab
Congratulations this week go to John Fischer, Dan Moore, Harry Fanning, Narciso Gomez, DeAnn Maddox and Karen Bartek, who were the first to correctly identify the April 18 location. Honorable mentions go to Casey Heck, Debra Brand, Ron Bartek, Angie Thomas, Subashini De Silva and Mike Martin. 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 25: JAG Run-A-Round