Jefferson Lab Weekly Briefs January 23, 2008

Jefferson Lab Weekly Briefs

January 23, 2008

12 GeV Upgrade

A full-scale, wooden mock-up of a segment of the planned Hall B CLAS12 has been constructed in the physics storage building (see 12 GeV Updates page) mimicking two coils of the torus magnet and one sector of the Region-II drift chamber. The mock-up has been used so far to test Region-II drift chamber mounting and to verify maintenance access and will be used to optimize cable routing. Regions I and III will be added to the mock-up in the future.


Hall B continues to run the Frozen Spin Physics Program with the FROST polarized hydrogen target. The target continues to operate very well at high polarization (80 percent on average). At the same time, linearly polarized photons are being used to measure double and triple (for strange particle production) polarization observables as a means to search for yet undiscovered new baryon resonances.

Free-Electron Laser (FEL)

FEL staff has made good progress on processing the gun test stand gun cathode structure over a 24-hour schedule, processing to more than 415 kilovolts (kV) on the high-voltage power supply. An automated processing script that has made HV processing an easier and more controlled process has also been commissioned. Also, good progress is being made in getting the Master Laser Personnel Safety System wiring completed.

Theory Center

The Deeply Virtual Compton Scattering (DVCS) process allows us to study Generalized Parton Distributions (GPDs) of quarks and gluons in nucleons and nuclei, thereby helping us to construct three-dimensional images of their internal structure. Modeling nuclear GPDs in terms of proton and neutron GPDs, a recent paper (arXiv:0801.3235 [nucl-th]) calculated the so-called beam-spin DVCS asymmetry for a wide range of nuclear targets,and considered the cases when the target nucleus is intact (coherent process) or when it excites or dissociates (incoherent process). The JLab DVCS experiment on helium-4 will be able to test these predictions in both the coherent and incoherent regimes and thus constrain the poorly-known neutron GPDs, as well as probe modifications of nucleon GPDs in the nuclear medium.


JLab's Safety Numbers

126 Days since Last Recordable Accident (JLab record: 319)
445 Days since Last Lost Workday Accident (JLab record: 455)

JLab Calendar of Events

Jan. 25: American Red Cross Blood Drive, 10 a.m.- 4 p.m.
Jan. 25: JLab 12 GeV Adopt-A-Spot Litter Pickup
Feb. 2: Virginia Regional High School Science Bowl
Feb. 6: Colloquium, CEBAF Center auditorium, 4 p.m.
Feb. 18: Presidents' Day Holiday (JLab closed)


Adopt-A-Spot Litter Pickup event on Jan. 25 
The 12 GeV Upgrade project team, along with ESH&Q staff, seeks volunteers to help with litter pickup along the sidewalk and grass areas from Onnes Drive to the corner of Jefferson Avenue and Oyster Point Road. Participants will meet in the CEBAF Center lobby at 11:15 a.m. for a short safety briefing and will then proceed to pick up litter. If you would like to participate, contact Cindy Saban at x5981 or in advance.


Environment, Safety, Health & Quality

Several recent local winter weather events point out the importance of being aware of what specific winter weather terms actually mean. Knowledge of winter forecasting terms will provide information as to which driving conditions to expect. The following is a brief description of winter driving forecast terms and their meaning:

  • Winter Weather Advisory - conditions such as cold, ice and snow are expected to hinder travel, cause significant inconveniences or create other types of hazardous conditions.
  • Freezing Rain - expected rain is likely to freeze as soon as it strikes the ground, causing an ice coating on roads.
  • Sleet - rain drops that freeze into ice pellets before reaching the ground.
  • Winter Storm Watch - severe winter weather is possible.
  • Winter Storm Warning - heavy snow, sleet, or freezing rain are expected.
  • Blizzard Warning - heavy snow, winds, and dangerously low temperatures are expected. Blizzards can reduce visibility significantly and produce life threatening wind chills.

Armed with the knowledge of expected conditions, you as the driver can answer one of the most significant questions regarding winter driving: Is this trip necessary? There are many options available prior to a trip in these weather conditions. Can the trip be delayed until road crews have improved traction? Can multiple trips be combined so that exposure to the traffic environment is diminished.


Welding of Exotic Alloys Lesson Learned
A recent lesson learned from Idaho National Laboratory (INL) emphasized the importance of reviewing standard welding practices in light of the availability of advanced corrosion-resistant alloys. Common corrosion-resistant alloys, such as 300 series stainless steel, are commonplace and well understood. However, more exotic alloys (super alloys) have become available and are being selected by designers. The welding practices that have succeeded in welding stainless steel may not be sufficient to produce higher-quality welds in the new alloys.


INL staff used standard welding practices for a proprietary alloy (high in nickel, chromium and cobalt content for corrosion resistance and elevated temperature strength) in vessel fabrication. Initial welding attempts were not completely successful, due to tensile strengths failing at less than minimum strength. Also, problems were encountered with heat treatment processes. INL analyzed these welding problems as resulting from the "super alloys" allowing design vessels to operate in previously unachievable environments. INL followup actions included allowing welders to practice on new materials to become familiar with their characteristics and exercising great care with heat and cleanliness controls. For additional JLab-specific welding information, contact Brian Murphy of the Quality Assurance and Continuous Improvement Department at x5515 or

Computing and Networking Infrastructure

Automatic Installation of Microsoft Office
On the evening of Feb. 5, the Computer Center will automatically install Office 2007 on all JLab Common User Environment (Computer Center-managed) Windows systems that haven’t already installed it. *Non-Windows systems, including Unix-based systems such as Mac OS X and Linux, will not be affected.* To sign up for training in the new features of Office 2007, see the announcement. As always, should you encounter difficulties with your computer, call or visit the Computer Center Help Desk, x7155 or CEBAF Center F200.


E-Mail changes to impact users of Pine, Mutt and mailx clients
Changes are being made to JLab's e-mail environment to improve e-mail performance and manageability. The first phase of changes will be implemented on Feb. 5 and will directly affect those who use text-based e-mail clients on Unix systems. Examples include Pine, Mutt and mailx. These changes will likely not affect those who use Thunderbird, Outlook, Mozilla, or other e-mail clients that use the IMAP protocol to read mail.

The changes that will take place are two-fold:

  • The mail spool directory (/var/mail) is currently mounted on all central user login machines, as well as many CUE level 1 linux desktops around the site. This access is being removed. This means that users of Pine, Mutt, or other text-based e-mail readers in Unix systems will need to configure these e-mail readers to use IMAP to access e-mail. Access to e-mail on the local file systems will no longer be permitted.
  • Some advanced users have their inboxes stored in their home directories in a file called mbox. These users will have their inboxes migrated back to the mail spool directory. This change will be transparent to all users that use IMAP e-mail clients. 

Additional changes that will affect all users and where you store your e-mail folders will take place later in the spring/summer. Announcements will be made regarding those changes at a later date.


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