Jefferson Lab Weekly Briefs
February 18, 2009
The accelerator performed reasonably well, with a continued low trip rate. The injector Wien angle was changed to optimize beam polarization for all three halls after Hall A was changed from pass 1 to pass 5. Vacuum valves VBV1L04A and VBV1L04B closed several times, most likely due to an internal leak of cryomodule 1L04. The vacuum has stabilized itself.
Free-Electron Laser (FEL)
The FEL team had a good week in getting to continuous wave lasing with moderate average power at short wavelengths (0.9 microns). The team is still working to increase gun cathode life. The cathode seems to be getting vacuum loading from downstream, which gradually kills the quantum efficiency. FEL staffers are working the transport setup and injector settings to resolve a low-energy tail in the beam distribution that leads to halo interception before the wiggler.
A new theory paper (arXiv:0902.0780 [hep-ph]) estimates the nuclear medium modifications of the quark contribution to the bound nucleon spin, Jq*, and the quark helicity, ΔΣ*. It also estimates the orbital angular momentum, Lq*, contributions to Jq*. The calculation is based on a model of bound nucleon GPDs that uses as input the bound nucleon elastic form factors predicted in the quark-meson coupling model. The medium modifications are found to increase Jq* and Lq* and decrease ΔΣ* compared to the free nucleon case, and the effect is large and increases with increasing nuclear density.
The RF group has a request for best and final offers out for the 12 GeV klystron procurement; responses are due shortly. The DC power group has issued a request for information for vendors interested in new power supply procurements for 12 GeV. The Alignment group re-positioned the Hall C beamline chicane components to facilitate the 5.9 GeV energy requirements of the Spin Asymmetries of the Nucleon Experiment (SANE).
A Special Message from the Worker Safety Committee
2009 Benefits Open Enrollment Is Underway
U.S. Postal Service Mail Delivery at JLab
Shipping & Receiving has been accepting and sorting incorrectly addressed mail, totaling approximately four to five crates a day. Most of this is catalogs, sale flyers, newsletters and similar third-class bulk mailings (e.g. junk mail). Shipping & Receiving cannot continue to handle this volume of incorrectly addressed mail. Starting on March 2, incorrectly addressed mail will be returned to the sender.
JLab's Safety Numbers
44 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Feb 20: 12 GeV Adopt-A-Spot Litter Pickup Event
Environment, Safety, Health & Quality
Jefferson Science Associates, LLC, was recently recognized with a Perfect Record Award by the National Safety Council. This award was given for safe operations during the period November 11, 2006 to September 10, 2008. This equates to 2,740,858 hours worked by employees, users, and subcontractors without an occupational injury or illness involving days away from work. In order to be recognized, the National Safety Council requires that companies, units and/or facilities complete a period of at least twelve consecutive months without incurring an occupational injury or illness that resulted in days away from work or death.
A new chapter on the Safety Warden Program was recently incorporated into the ES&H Manual, as well as two revisions to the Environmental Program. All recent changes are listed below:
Computing and Networking Infrastructure (CNI)
E-mail Outage and Reconfiguration, Friday, March 20, 10 p.m. Through Saturday March 21, 3 p.m.
The location of e-mail folders is being changed; e-mail folders will be moved to a new location. Currently, JLab account holders have e-mail folders that are stored in their home directory (/home/user on Unix or J: drive on Windows). The reconfiguration will move these folders out of account holders' home directories and place them on a standalone, isolated file system. Account holders will not have direct access to this new file system. All access to these folders will require an IMAP mail client (i.e. Thunderbird, Pine configured as an IMAP client, etc). Further information about this reconfiguration will be available on the CNI group web page as the date approaches.
Windows Common User Environment (CUE) Software Refresh